Birth of Serpents
by hotmilkytea
Summary: [2012, AU of Vengeance is Mine] The Shredder succeeded in mutating the turtles into vicious snakes. Now Karai needs to turn them back, before it's too late.
1. Part 1

an AU in which Karai did not fall into the mutagen back in Vengeance is Mine. standard disclaimer applies, TMNT is Viacom's and I get nothing from this.

* * *

 **Birth of Serpents  
part 1**

* * *

The last Hamato Yoshi saw of his sons is not how he would choose to remember them.

His boys, looming over him like a group of hydra, hissing and snapping before, one by one, they broke off and fled into the night. Perhaps he should be grateful for that, that they did not set upon him with fangs and venom, that they still understood the base concept of filial respect.

Perhaps they were simply afraid.

He remembers too much of his own mutation: his anger, his _fury_ , at being warped into something so obscene. Most of all, he remembers being afraid — this was not his body, these were not his children. And while his sons are already mutants, he cannot accept the idea that they would lend themselves so easily to this — to a forced mutation, their bodies stolen from them and twisted to another man's purpose.

It is a sick sort of duality that this is the second time in his life he has lost a child, that his brother ruined his life to the soundtrack of fire, that his brother's laughter has risen above the flames.

Worse, there is now a thick weight in his stomach that there is something greater at work when it comes to his children: that he can have one, or the other, but never both. He will always be forced to choose — between the daughter who was stolen from him, and the sons who were forced upon him. Of course he sees his sons now for the gifts they are, but back then they had been four angry little mouths to feed, in a world that would hunt them down rather than look at them as marvels.

And though he loves his daughter, for all that she was as a baby and all that she is now as a young woman, he can already see things that need to be stamped out of her, to erase any trace of the Foot in her soul.

He loves them all equally, as a father should, and yet…

And yet.

And yet it does not become him to give up so easily. No, there needs to be a plan, he needs to _try_ , before he gives himself over to grief.

He senses Miwa before he hears her, an awkward presence just beyond the doorway to the dojo, but he does not summon her. This is something she needs to learn as part of this family — he will never demand her presence, but accept it when freely offered. "Father," she says, a few minutes later, her feet padding gently onto the old rugs. The word sounds hesitant in her voice, as though she is unsure of her right to claim it. "What do we do? We can't just let them—"

"You should rest, my daughter," he says, interrupting, though he knows full well that Miwa will not. "Tomorrow, we will find them."

He hears her begin to form a protest, and the silence of it dying in her throat. Quietly, Miwa turns away and leaves, closing the shoji behind her.

It is to be a long night.

* * *

" _Hey," Leo said, lopsided and wry as he prised the cage open with a dagger he slipped from the pommel of his daito. "You okay?"_

 _Karai was breathless, winded from the fall, but she managed a "yeah" as he eased her to her feet._

 _Above, the Shredder watched them. She bared her teeth. "Give me a sword," she demanded._

 _For a heartbeat, Leo watched her, his gaze calculating and hard, before he nodded and unsheathed his short sword. Karai weighed it in her hand — it was heavier than her own blade, and wider; the craftsmanship was good, but not_ that _good. Then Leo jerked his head, and Karai slipped into battle at his side._

 _Across the room, Leo's brothers were fighting next to their father, freed from their tiny cages as they took on Footbots, as Tiger Claw snarled and hissed and spat and shot._

 _Karai faced the tank, and leapt upwards._

 _Leo had shown off to her enough in the past that she knew his style: the intent in the tightening of his muscles before he struck, the sly finesse, the times when arrogance gave way to_ skill _. As they fought their way towards the Shredder, together, Leo made room for her, so keen to make sure that she felt like she belonged in his weird little family — in_ her _weird little family._

 _A few weeks ago, she'd have found it pathetic — sad, needy Leo, letting his heart get away from him, determined to be the good son while defending a_ murderer _, defending a_ monster _. He could have been_ great _; instead, he chose to stay with those freaks he called brothers, protecting a city that didn't want him and a man who had killed a woman in cold blood._

" _On my left," Leo said, twisting away from a Footbot, and Karai beheaded it._

* * *

The kitchen in the lair is small, smelling faintly of industrial bleach, mildew, and the too-sweet, too-damp stink of compost.

Karai throws the cup of tea she'd made for Splinter down the drain, and slams the chipped old mug down on the counter. Small pieces of leaves spatter the sink like mud, and for a long moment, Karai curls a hand over the edge, squeezing until her fingers and knuckles hurt.

It's too quiet.

The lair feels like a living thing, breath baited, waiting for the brothers to come trooping home, too loud and too noisy, high on the thrill of victory.

They are not coming home.

They did not win.

* * *

 _Mikey started the fire._

 _It was accidental — Tiger Claw seized his kusarigama in one massive paw and yanked hard, swinging him out of the fight and into the oil drums. Then, Raph mashed a Footbot, and the sparks caught on debris. The church, derelict and old, lit up._

 _Karai didn't care. She and Leo had fought their way to the Shredder, and the ghost of her mother was shrieking for blood. Karai had only been told fragments of a warped story, but these she knew, and still knows now: that Shredder murdered her mother, that he stole her away, and that he left her father to burn. Tang Shen lay buried halfway across the world, and Karai had sworn on her grave for the past fifteen years that she would give her mother the revenge she deserved._

 _It would end_ tonight _._

 _Leo feinted, and Karai surged in his wake. Leo's sword was heavy in her hands; it made her strikes slower, but when she slashed at the man who killed her mother, he did not fight back with the viciousness he raised her with. The Shredder was not trying to kill her — and because he was not trying to kill her, he could not try to kill Leo. And Oroku Saki did not speak, except with his eyes. Angry, as he always was, and reproachful, as he had only been these past two weeks:_ My daughter, why don't you understand me?

 _He made Karai_ sick _._

 _Karai had been a weapon in his hands. Karai had been the poison in his garden, carefully tended, carefully grown, ready to harvest, and distill, and_ use _._

 _Karai was still a poison, but on the edge of her own blade. She was silent and slim, a dagger in a sleeve; whatever Oroku Saki said to her, she didn't want to hear it. This would end tonight. She feinted, this time, swift and to the bottom-right, to the side where his ruined eye couldn't see. Leo used his weight and speed to throw himself forward; the Shredder barely staggered before he threw Leo aside, but that gave Karai time to slash upwards, steel glancing off his armour and into scar tissue._

 _The Shredder let out a shout of pain. He lifted his arm in disbelief. The slice was not nearly as deep as Karai had hoped for. "Karai," he said once, voice low. His one good eye narrowed._

 _She wondered if her mother screamed, or if her mother had begged._

 _She tightened her sword. The man who used to be her father stared her down. Cloaked in the green glow of the tank, and red light from the flames, he looked like the monster Karai now knew he always was._

 _Leo was at her side again. He glanced at her once, and she nodded, and both of their blades ready, they lunged for the Shredder's throat._

 _Below, Splinter shouted "NO!", and Leo stopped. Everybody stopped._

 _Donnie was screaming._

 _His hands covered his eyes, but it was too late._

" _No," Karai heard Leo say, over the clamour of his brothers. Donnie's voice rose to a howl, hollow and alone, his hands clapped to his face as the glow burst through his fingers. Leo dropped his sword and ran. "No, Donnie!"_

 _The tank had taken damage in the fight, great cracks running up the glass. A broken Footbot lay at the base, mutagen spurted out of the tank in ugly, pressurised gushes, and as the turtles ran for their brother, he fell to his knees._

" _Stay back!" Splinter ordered. His three remaining sons hesitated, and even Karai felt obedience jolt down her spine._

 _But Karai could tell, from the way they fought together, from the easy affection, from the way they looked at each-other, that the turtles had never been apart from each-other for more than an hour in their whole lives. They were not four brothers, they were one_ family — _one_ whole _._

 _This was an order they couldn't even understand._

 _The three of them surrounded their brother while Tiger Claw kept their father away, their hands caught between grabbing for Donatello and fending him off. His shrieking came in great whooping gasps as he tried to force his way through the_ burning _, to tell his brothers how to fix this, and tried to tell them to get away from him. Karai expected some sort of flash of light — something instant, something quick; that Donatello would blink out of existence and reappear reformed._

 _Mutation is not quick._

 _Donatello's shell cracked and melted at the same time, reforming into a long, rippling spine. His face caved in on itself and reshaped to something more serpentine, fangs forced their way out of his mouth, and what used to be his hands broke at the wrists and bent backwards as eyes rose from his palms._

 _In the eerie silence that followed, this new mutant threw back its heads and hissed, and Splinter said, very quietly, "My boy"._

 _At Karai's side, a foot away, the Shredder was laughing._

 _What used to be Donatello hurled itself at Leo and his brothers, heads snapping, mouths shrieking, and it wound around them all. All four of them together._

 _Karai knew, then, what was going to happen next._

 _The Shredder raised his foot, and slammed it down on the edge of the tank._

 _The glass made a sound like calving ice, and then Leo and his brothers were washed away._

* * *

 _The mutagen flooded the room, howls twisting into hisses and the slither of scales on tile. The turtles rose up as one, twelve heads hissing and snapping before lunging at Splinter. Tiger Claw threw himself back, ready to watch the turtles do the job Shredder had assigned them — to tear Splinter apart, piece by piece, until their father's blood was in their mouths._

 _Karai couldn't tell them apart. There were no warm smiles or shared looks, and if one of them looked a little longer, a little sleeker, a little thicker, it only lasted a second, before they slithered away, their bodies roiling and their eyes green and vicious._

 _They were hungry, Karai thought. Hungry, and angry._

 _Karai grabbed for the nearest piece of wood — Donatello's abandoned bo, and held it into the flames until it caught fire. She swung it, the flames trailing around her, and as she jabbed it towards each snake, it flinched, slinking back with its smaller heads snapping. "Back. Get back!" she snapped, and they slowly inched away, one of them swirling up around a roof support and watching from on high._

 _Behind her, Splinter wheezed, a hand covering his nose from the smoke, and the snakes watched, tongues flickering. Karai could hear it over the clatter of roof tiles and crackling wood. She held the bo staff still, in warning. One by one, they turned, throwing themselves towards the nearest exits — one to the left, two to the right, one throwing himself past them and out through a window._

" _Miwa," Splinter said. "We must leave."_

" _But—"_

" _They are gone," he said. Grief made his voice weak, and Karai forced herself not to look away._

 _Dropping the bo, she drew Leo's sword again and landed in front of her father. Splinter's muzzle curled up in a snarl as he looked up to where Shredder stood on high, his armour glinting in the firelight and his cape fluttering in the unnatural wind._

 _The man she had called father, once — the man who had commended her on her first kill, who had taught her how to walk and how to throw knives, who had worshipped the memory of her mother almost as much as he revered the honour and history of their clan — the man who had murdered her mother and destroyed those who could have been her brothers._

 _He raised an arm in the direction two snakes had fled._

" _That's right,_ rat _. Leave your sons just as you left your_ daughter _! And when they come for you — and they_ will _come for you — remember who it was who finally put an end to you, and your wretched clan."_

* * *

The lair is too quiet with only two people living in it.

As the night passes, it becomes beyond clear that Karai will not find any sleep here. Not while Splinter still meditates in the dojo, not while the turtles roam the streets, not while the peace she had expected to feel at Oroku Saki's death is swallowed up by the rage that he is still alive.

She decides, eventually, that one of the turtles won't mind if she borrows a bed for the night, instead of the small, uncomfortable futon she had abandoned the night before. The other side of that — _they wouldn't even notice —_ is a thought she throws away the second it rises. They would notice, because they are ninja. They would notice, because they are going to come home, and Karai will smile and say _thanks_ , something she's getting better at. They'll come home, and she'll ask, _so, where's_ my _room?_

When they come home.

When Karai _fixes_ them.

Karai is not used to feeling guilt. The Shredder did not raise Karai to feel it, and she has never had time for it. So, in the quiet, where there are no brothers arguing, no yelling for someone to go to sleep, no snoring, no quiet pride in her father's voice, it takes her a long moment to understand that the weight around her heart is not just regret, or sorrow, or loss.

Karai knows all three, but this is not the same.

What the Shredder taught her, though, was _revenge_. He taught her retribution. He taught her how to take a situation and _fix_ it, through whatever means necessary. The Shredder taught her determination, above all other things.

So Karai will fix her brothers, no matter the cost.

She wonders when, and how quickly, it was that she started to refer to them as _her_ _brothers_ , rather than _the_ _turtles_.

Leo's room is the only one not half-way towards _teenage boy hell_ — his bookshelves are neat to the point of neurosis, and there's a little shelf full of sword-care stuff, like wraps of spare leather, and powder for the blades. But his towel is dumped on the floor along with a sweat-stained bandana, there's half a set of Guitar Hero in one corner, and there's a pizza box shoved haphazardly under the neatly-made bed.

Karai sits on it, patting the covers once before flopping down onto it, her legs hanging over the sides.

The strategist in her tells her that Leo sleeps on his back; the indent in the mattress beneath the blankets can only be from his shell. He probably lay here while planning, deciding how to come up against Tiger Claw, and what if Bradford had been there? Would Mikey go up against Xever, or Donnie?

When Leo and his family arrived to save her, they had a _plan_.

Topside, New York will wake up to a new day. The newspapers will talk about the President, the TV about that fire across town, and Karai's brothers will be lost, twisted, alone and mindless, mutated far beyond their forms to a place beyond her reach.

She turns, burying her face into Leo's pillow.

Leo would make a plan.

Leo would get them _back_.

* * *

 **tbc.**


	2. Part 2

next part! thank you so much for the reviews/follows for part 1 - you're all lovely, and I'm so grateful!  
TMNT belongs to Viacom.

* * *

 **Birth of Serpents  
part 2**

* * *

 _When Karai was very young, back before she knew that Hamato Yoshi was still alive, before the Shredder took her to a foreign land to write the ending to an old, old tale, someone tried to rise against the Foot._

 _The Shredder had been furious, and Karai had watched as his underlings delivered the news, cowering beneath his wrath. Bradford was visiting, and Karai had hidden in the shadows as he and the Shredder planned their counterattack._

 _When Bradford eventually left the room, the Shredder had turned to her: "Karai, you should not be here."_

 _She peeled herself out from her hiding place, moving as quietly as she could across the floor until she stood by his side. The Kuro Kabuto had been set aside, and in the dim light, the ugly red scarring on his face looked angry and sore. "I'm not tired," she said, peering over the table at the documents, the maps, the small tactical toys. "What did they do?"_

 _The Shredder did not answer, at first. Instead, he sat in the oak chair at the head of the table, and Karai slunk over, crawling up into his lap. "Father?" she prompted, and he made a heavy sound in his chest._

 _"One day, all of this will be yours," he said, nodding to the papers and planning work. A small kunai had been stabbed into a photograph. "but only if we_ protect _it."_

 _Even back then, Karai had felt the familiar surge of respect for her clan — the clan that had survived decades of disrespect, that was clawing back its_ honour _by the fistful, reclaiming its land, reclaiming its heritage, avenging its losses and casting out new lines to ensure it survived. The Foot would no longer be condemned to be a footnote in a hidden history; instead, it would evolve, modernise. From the shadows the ninja thrived in, it would forge a new era._

 _But only if it protected itself._

 _The Shredder's heavy hand settled gently on her head. "What must we do with our enemies, Karai?"_

 _Karai had smiled, reaching out, and wrapped her hands around the kunai's hilt: "Destroy them."_

* * *

The morning after the Shredder destroyed his enemies, Karai woke up, her mouth tasting like sewage and failure, and crept from Leo's room to see her father's silhouette unmoved — still meditating, still _planning_.

Hamato Yoshi is a lot slower than she expected.

If this had been the Foot, and the turtles loyal to Shredder, Karai would have woken up in the morning with her troops waiting for her orders. They'd have been briefed on a plan — the Shredder would have stayed awake all night _plotting_ , pulling out resource after resource in order to bring the turtles back, in cages if need be.

Karai would not still be _sitting here_.

"Father," she says, the word uncomfortable on her tongue. "What do we do?"

Splinter takes in a deep breath through his nose, then says nothing. He looks instead to the shrine, to the broken glass bowl on the shelf. The bowl means nothing to Karai, but beneath it, the picture of her mother stares back at her with unreadable eyes. Karai wonders what Tang Shen would do in this situation — what would her mother have done, if she needed to protect something she loved?

 _Die_ , Karai thinks. Her mother _died_.

That's not an option. Not for Karai.

"We wait," Splinter says, after a moment. "My sons will come home."

"What if they don't?" Karai answers, immediately. "You _saw_ them — they're not even turtles any more, they're _monsters_!"

Splinter flinches beneath the old robe he wears.

His sons are monsters, Karai realises, but they have always been monsters. Maybe not to him, but to the rest of the world, his family is a freak show. Splinter can't go above ground to find his sons, because he's no less a monster than they are. There will always be this line between her and her father and her father's sons. She can go where they can't, do what they can't. She can go look for her brothers. Her father cannot go to look for his sons. He has no _choice_ but to sit and wait.

She sucks in a breath that roils in her tight chest and opens her mouth to apologise—

—then shuts her mouth with a click. Someone is coming.

She turns towards the screens just as the turnstiles out in the den clatter.

" _GUYS GUYS why aren't you picking up your phones, didn't you—guys?"_

* * *

April has never come to the lair to find it empty. If the turtles aren't home, usually Sensei is meandering around, taking advantage of the boys being out to pick up in their wake, or work on his own training or, this one time, watching trashy CW shows. But the turtles would always come back not long after, a loud, clattering group who seemed to forget the whole concept of _ninjas are silent_ as soon as they got below ground. Sometimes they'd bring pizza, and sometimes they'd be hurt, but they would always come _home_.

Now, instead, April has to close her mind against echoes and visions of them: Donnie is not slouched over his sketchpad, and Mikey is not playing with Ice Cream Kitty. They're _gone_ , and what's worse, is that Splinter is going to just _sit around and wait_. The city is full of tunnels, he could have started there instead of coming back to the lair to lick his wounds and _meditate_ while the turtles, her _brothers_ , roam the streets topside.

Even with her anger to shield her, though, April feels sick under the weight of Splinter's grief. It's heavy, and dignified. Splinter has always been grieving, but instead of the thin winding brook of sorrow April is used to, it's a rain-flooded river now, full of mud and silt and blood and ash, and it's almost too much on top of her own.

But April's grief is a low-banked fire, and has been ever since she woke up in her aunt's spare room the morning after she lost her mother. Splinter will let his grief run its course, but April can _use_ hers, and this, at least, is one thing she can try; maybe this will give her a clue, _any_ clue, as to where they might be. The newspaper front page — _GIANT SNAKES TERRORIZE MANHATTAN_ — is left abandoned on the kitchen table. She can't even look at it right now. Instead, she's looking at Donnie's laptop. He'd left it in the kitchen, next to a cold mug of coffee and a half-eaten piece of algae-on-toast — _Donnie_ , she thinks, her heart twisting.

Karai slides in, leaning up against the kitchen counter. "So," she says, her voice smooth and prompting.

April ignores her and wraps her ankles around the stool as she types, trying to ignore the fingerprints all over the screen as the computer homes in on three blinking signals.

Just three, in the heart of the Shredder's lair.

April doesn't know what she was expecting.

Karai walks over, leaning into April's personal space. April can hear her breathing, and forces herself not to lean away. Karai doesn't _get_ to see April being weak. "Did you try—"

"Yes," April interrupts, impatient, her hands flying over Donnie's keyboard again. "I already tried finding their phones. Maybe you should ask your dad if you can have them back."

The spark she feels in Karai's mood is vicious, and April squares her shoulders ready for the fight — she's _spoiling_ for it, she realises, her anger twisting in her shoulders. Karai was there when it all happened, Karai was the _reason_ it happened. If it hadn't been for her— if she hadn't—

April has spent a lot of her life angry. April has spent a lot of the past two years hating things; real, actual, cold hate, the type that leaks into cracks and freezes and breaks things apart. Karai turned her dad against her and _laughed_ about it — April hates Karai. _Hates_ her.

She hates Karai even more when she refuses to rise to the bait. Instead, Karai picks up the newspaper, looking at the front-page picture of the damage done around Bleecker Street. She turns away from April when she says, "Shredder is _not_ my father."

April swallows down the knee-jerk need to say something back that will hurt, and lessen the building pressure in her own chest; that Karai is here, and the turtles are not.

She can scream at Karai later. Now she needs to _work_.

While Karai reads the newspaper, April brings up every report she can find of giant snakes: slithering through the storm drains on Delancey, smashing through traffic on 34th, wrapping themselves around subway trains before disappearing into the dark.

Splinter said that they didn't recognise him. That they'd fled, each one of them alone, into the night. She wonders if that means that they didn't recognise themselves. If it means that if she finds them, they won't recognise _her_. If the snake has taken over completely, or if they're just locked in their own heads — because they mutated again, but that doesn't mean they're not who they used to be, does it?

She doesn't exactly want to go to the Foot to ask Chris Bradford his opinion on the matter.

She definitely doesn't want to ask Karai anything about the Foot, either.

Besides, she needs to find the turtles, first. Before anybody else does. Before Shredder does and turns them into his personal attack pets, or worse, the Kraang, or _worse_ , the _government_.

"You got a license?" Karai asks, in that sly, smug way that sounds like she's answering her own question: _of course you don't; you can't drive, you can't_ fight _, what_ can _you do?_

"No," April says tersely, sending a map to her t-phone. "I don't. I'll walk if I have to."

"Or," Karai nods out towards the lab. "We can take Leo's truck-thing."

 _Donnie built it_ , April wants to say, but the words tangle like thorns in her throat. Donnie built it, Leo drove it, and Karai has no right to take _anything_ of Leo's.

"It'll be quicker," Karai adds. "And if we find one of them, we can bring them home."

April doesn't ask how Karai plans to do that. Karai does what she wants. April knows what to expect with Karai: defiance, and envy, and vengeance. It's been that way since the day April met her, when she dropped the act as _Harmony_ and tried to kill her in broad daylight.

This time, though, when she listens to what Karai is not saying, the malice in Karai is not aimed her way.

"Fine," April says.

* * *

Karai takes Leo's seat up front. The keys are still in the ignition — nobody comes below ground to steal assault trucks, she supposes — and as O'Neil slides into a seat behind her, the truck snarls to life.

"So where first?" she asks, then scowls when she gets no reply. "Hey. Princess."

" _Don't call me that._ "

"Alright," Karai says, with a shrug. "O'Neil. Where should we head first?" She doesn't get a reply, and Karai turns to look over her shoulder. "Hey. O' _Neil_."

O'Neil has her hand over her mouth, and she looks like she's trying not to cry through the sheer force of being angry as she looks at the monitor in front of her.

Karai doesn't roll her eyes, because Karai _gets_ it, but there's a time and a place for this, and it's not right now. Still, she walks over, because she and April O'Neil have never really been anything close to friends — Karai has never _wanted_ to be her friend; April O'Neil, centre of an alien invasion, best friend to mutants, who thinks she's cute because she knows how to use a pair of chopsticks — but they're the only two, right now, who can _do_ anything. Crying's not going to help.

The wallpaper on the computer screen is a group shot: all four turtles and Splinter, in front of the dojo tree. Karai scowls. It's a sweet picture. A family portrait. Everyone looks happy, and healthy, and normal; they look so _pleased_ with themselves. Maybe the picture was taken after a fight, or a holiday. Maybe they just wanted a picture to prove what a nice happy family they all are.

Before Karai gets a chance to analyse the little spark of envy in her chest for what it really is, O'Neil sucks in a breath through her nose and brings up Twitter, running a search string for snakes in NYC. "There's been a sighting on FDR," she says, pointing at the screen. Her voice is rough. "There's a junkyard there that they sometimes go to."

Karai doesn't know why she's surprised that the giant truck with an ice cream lamp also has 3G. "FDR, then," she says instead, and slides back into the driver's seat and puts the truck into gear before O'Neil can say anything else.

* * *

New York is weird enough that a graffiti-clad assault tank doesn't turn too many heads as Karai drives out of the subway and onto the streets, but she still can't help but feel conspicuous. It makes her uncomfortable — she's used to blending in, into shadows at night, and into crowds during the day (even back in Japan, where her hair just made people think of her as a punk kid rebelling for the two years before she faded back into mediocrity). And even with sunlight spilling through the graffitied windows, it does nothing to ease the chill in the air.

Karai doesn't need to turn around to feel the scowl. It's there, on the nape of her neck, sitting just above the tightness in her shoulders.

"Splinter says he doesn't blame you," O'Neil says, when the silence gets too much. Karai grits her teeth and focuses on driving, her fingers curling around the wheel of Leo's glorified junk heap, so that when the inevitable follow-up — "but _I_ do" — comes, she had something to occupy her hands that wasn't ripping out handfuls of O'Neil's hair.

"Well, you're wrong," she snaps curtly, and watches how O'Neil's face scrunches up in the reflection of one of the screens. "Shredder's the one who did this, so Shredder's the one who's going to pay for it."

No reply comes to that, and Karai feels almost cheated. She was never going to get along with the turtles' special little princess, but she was at least hoping that she'd be _smart_.

"You know," Karai says after a pause, "I have better things to do with my time right now than kill _you_. So why don't you work with me, here? We're both after the same thing. You want the turtles back, and so do I."

O'Neil doesn't say anything, except, "Take a right."

* * *

They find nothing at the junkyard — no scales, no slithering tracks, just a creep who wanted to know what two nice young ladies were doing at the dump all alone. All the places from the news are a bust — the Chinatown gate, the storm drain at the corner of Bowery — so O'Neil directs Karai to the noodle place on the edge of Chinatown, instead.

Even for a blind old man, the guy at the noodle store _recognises_ Karai as she walks in behind _April-chan_. He pulls O'Neil aside, asks a question while palming his stirring paddle, and doesn't stand down until she says, _it's okay, she's with me_. Even then, he's still wary, but Karai guesses she can deal with that considering what happened in here the last time.

He hasn't heard from the turtles, but asks them to return Michelangelo's phone, the battery long dead from the last time he left it here.

Karai waits outside while he packs up some free food, and is kicking her heel against the beaten old vending machine when O'Neil comes down the steps.

"Knock it off," she snaps, and Karai rolls her eyes.

"So they're not here."

"What part of the _giant killer snake_ did _you_ see in the noodle bar?" O'Neil shoots back. Karai is about done with the snappy princess routine. She kicks off the vending machine, ready to tell April O'Neil exactly what she _should_ be focusing on, then stops.

O'Neil looks _miserable_.

At least now they have two things in common.

O'Neil rubs a knuckle between her eyebrows. "We checked the junkyard already, we checked Murakami's — I don't know where else they'd be, not during the daytime."

"The docks?" Karai offers — it's the only place she's ever seen them in sunlight. O'Neil shakes her head.

"No," she says eventually. "They'd only go there if they have a reason."

"That's assuming they have any reason." Karai hates the idea, but Karai also saw how all four of them rose up, hissing and spitting. They hadn't recognised her. They hadn't recognised their own father, and they had escaped into the night, each one alone. It's not difficult to assume that the turtles are just _gone_.

O'Neil is rubbing her fingers against her temples, her brows knitted together. "I don't know where they are," she says, after a moment. "I can't—"

Karai raises an eyebrow, but says nothing. "We _could_ go back to the lair," she offers, but it's a lame offer. It feels like admitting defeat — that she couldn't find them, even in broad daylight. "Or—"

For the second time that day, Karai is cut off, this time by the loud, brash guitar riff of a terrible rock song.

"Oh no," O'Neil moans, her face creasing as she pulls out her ringing phone. She sucks in a deep breath, schooling her face into something halfway between determination and grief, and slides her thumb across the screen. "Casey, hey," she says, holding the phone out on speakerphone.

" _Hey Red. So, uh, how are things?_ "

"Not good." She pauses, glancing in Karai's direction. "Where are you? Did you see the news?"

" _Yeah,_ " Casey says, his voice strained. Karai raises an eyebrow that O'Neil ignores. _"About that. Funny story. So, uh. I tried to call Raph but he's not pickin' up — there's kind of a... giant snake mutant. Outside my apartment."_

* * *

 **tbc.**


	3. Part 3

I am so so stunned and grateful for the lovely comments and favourites and messages I've gotten about this fic. thank you so much, I'm so happy you guys are excited and seeing where you think the fic is going makes my day :D

next up: a turtle returns home.

* * *

 **Birth of Serpents  
part 3**

* * *

Casey Jones has seen a lot of weird shit in his life. Like, _a lot_ of _weird shit_ , and that was before his best friend was a giant turtle and the chick he was into turned out to be a psychic half-mutant alien who didn't get hockey, and who listened to crappy indie bands that ate organic and danced barefoot. He's from New York City, and lived through the Alien Apocalypse of 2013, and fought off a giant glass tank of _human organs_ using just his bike and his extremely good looks — _he has seen some shit_.

This, though, pushes the shit-o-meter straight from _holy crap awesome_ to _what._

Slowly, he closes the curtains. Looks at the cloudy glass of water next to his bed, and the empty bag of cheese balls he ate the night before. Looks back at the curtains.

Opens the curtains again.

The snake is still there. Still coiled up, still with its face pressed all needy against the window. "Yeah," he says, couching his cellphone between his ear and his shoulder. "I'm pretty sure. So, whenever you wanna get the guys and get over here, that'd be great."

* * *

There's nothing fancy about Casey's apartment. It's on the edge of the East Village in a rent-controlled building where half the residents are waiting to die. The hallway smells like dust and old people. But the super's a nice guy, and when he sees April — and _friend_ — he waves both girls up to the Jones apartment, on the fourth floor. Once April manages to sweet-talk her way past Casey's dad ( _good morning Mr. Jones, isn't it a great Saturday? We have a trig exam on Monday and Casey said we could come over and study— this way? Thank you!_ ), she and Karai slide through the bedroom door with a skull carved into the wood to see Casey, in a t-shirt and ratty boxer shorts, slumped on his floor, encircled in a large coil of mutant snake.

The snake is asleep.

The snake also looks incredibly comfortable, the main head flopped gently in Casey's lap and the other two curled around his arms.

April stares. "Casey, you _let it inside_!?" she snaps, her hands rising as though not sure whether to defend herself or wring Casey's neck.

"He started _whining_ ," Casey hissed. "I didn't even know snakes _could_ whine. So I opened the window to see if he could talk, and he just _tackled_ me. And then he _hugged me._ "

He says _hugged_ like the concept mortally offends him: Casey Jones, professional badass, freelance vigilante, snake snuggler.

April shoots a careful look at the door, but Karai has already moved to block it. "Well," April says, rueful, but the humour falls flat even as the words hit the air. There's nothing funny about this; there never will be. "I think we've found Raph."

* * *

It takes a good ten minutes to get Casey up to speed, and into some pants. Through it, he watches Karai like she's about to knife him, and rests a hand protectively over the snake's biggest head. "Okay," he says slowly. "Raph, I get. The whole thing with the turtles— _sucks_ , but I get it. What is _she_ doing here?"

"She's on our side now, apparently," April replies, leaning against Casey's desk.

"Yeah, but — _that's Karai_."

"I _know_ that's Karai. Leo busted her out, and now she's not with the Foot."

"And she's standing right here." Karai folds her arms. "Are we seriously going to have this conversation every time I meet one of your little friends, O'Neil?"

"Gee, I don't know," April snaps back. "Why don't we go see my dad after we're done here, how about that?"

Karai smiles, dripping insincerity. "Yeah, I'm not so big on reunions," she says. "Besides, he might call the Kraang to join the party."

April bolts upright as rage blossoms through her. "Say that again," she snarls, balling her hands into fists. Her tessen, tucked into her shorts, feels warm and ready to wipe that look off Karai's face. "Go ahead, Karai. _Say it_."

A flicker of movement at April's left and a flash of someone else's fury is all the warning she gets. Raph opens one acid-green eye, the snake's pupil split and narrow. Then he moves.

April doesn't know what she was expecting to happen. Splinter had told her, in heavy, weary words, what his sons had become, and what they had done. They had attacked and escaped, wild and untamed, but somehow April had still _hoped_. The turtles are her brothers in everything that matters, they protect her, they _care_ about her, in their own ways. But Raph rises up, his eyes narrowed and hungry, and all of his teeth are bared as he coils away from Casey and towers above them all.

He doesn't recognise her.

"Oh crap," Casey says. Raph spins away from them and towards the windows. He slams himself against the glass once, twice, the panes ringing dully and shaking in the frames, but they don't break. Raph rears back, looking almost _offended_ , before turning for the door.

Karai is in the way.

"Karai!" April yells. " _Move_!"

She doesn't. In Casey's small bedroom, there's barely space for _anyone_ to move, and April watches, pinned against Casey's desk as Raph reels towards Karai. He lifts himself up, and April forces herself to watch as all three sets of jaws lunge for Karai's face.

Karai leans back an inch, her face cold and impassive. Then, she brings her knee up and slams it into Raph's body.

Raph falls back, throats hissing, and in the moment he takes to collect himself, April catches Casey's eye.

He nods.

Both of them lunge for Raph. April clings to his lashing, furious tail as Casey wrestles him down. The smaller heads snap and spit, flaring out until Karai seizes a hockey stick and shoves it into their mouths. She holds it firm as Raph bucks, his whole body trying to shake himself free. "Casey, do something!" April yelps, trying to straddle Raph as Casey clambers his way along Raph's body to his head.

"I'm trying!" he snaps. Raph rears up again as Casey locks his arms around Raph's head and drags his face up. Raph hisses again, a phlegmy sound bubbling in his throat, and Karai manages to yell out " _Venom_!" as Raph readies himself to spit.

Casey scowls, screwing up his face, and headbutts Raph at full force.

Raph sinks.

In the absolute quiet afterwards, Casey's Andrew W.K. poster slowly untacks itself from the wall and drifts down to the floor. April can hear her own heart pounding in her chest, and feel it in her throat. Karai doesn't move, and Casey talks very quietly as Raph stirs: " _it's okay, buddy. It's okay._ "

And then someone pounds on the door.

Raph's head lifts up again, but Casey keeps a firm grip, running his thumbs along the ridges over Raph's eyes as he turns his head towards the door.

"Sorry, dad!" Casey hollers. "We knocked something over. It's— everything's good!"

Outside the room, Casey's dad grumbles something about _keep the door unlocked when you've got girls over_ , and his footsteps shuffle down the hall. Casey lets out a long, slow breath of relief, colour hot and high in his cheeks. April can feel her own face burning in embarrassment, whereas Karai looks as sleek and as unruffled as she always does. April supposes that's natural: Karai's got too much blood on her hands to be worried about being caught in a _boy's bedroom_.

Moodily, Raph winds himself around Casey again, his head flopping in Casey's lap for five seconds before nudging insistently, demanding to be petted. "Okay," says Casey again, gently scritching along the scales that run along the snake's — _Raph_ 's — head. "So we take him back to the lair, get rat-dad to— what?" he asks, when Karai shifts.

"I'm not so sure putting them in the same room as my father is a good idea," she says, and April can feel the worry that leaks out of Karai for the moment before she slams her doors down on it. "He's _food_."

Something tightens in April's chest; anger, and grief, and a slick, hot urge to strangle something. She hadn't considered that, that there was a _reason_ the Shredder had picked snakes as his next experiment. Turning the turtles into something that would hunt their sensei down is _sick_. "We don't have a choice," she says tightly. "We have to get the turtles below ground."

"Good idea," Karai says slowly, "but how do we get Sleeping Beauty there down to the sewers?"

April casts an awkward, uncomfortable look at the door to Casey's bedroom. "We could…" she begins, then trails off as soon as she sees Casey's face. Casey's dad is in the living room, blissfully unaware of the giant mutant in his home, and worse, his _sister_ is watching her cartoons.

"No way. My dad's not seeing this," he says, cutting a hand through the air.

"Okay, so we can't use the front door." April pinches her nose. "We could take him down the fire escape? The alley's pretty empty during the day, right?"

"Yeah," Casey replies. His voice is still blown out and breathless. "Nobody goes down there while I'm here." There's a thin thread of bravado in Casey as he says that, but there's none of his usual preening; he's just stating the facts. He looks after his turf.

Karai peels herself off of the door. "Alright then. I'll go start the van." As she slinks over to the window, she grabs Casey's bedsheets and hauls them along with her, before dropping them on the floor. "You better wrap him up. Don't want to give people too much of a reason to look, do you?"

* * *

As the window shuts behind Karai with a _snkt_ , April leans forward, fists her hands in her hair, and she lets out a long, frustrated growl.

"Red?" Casey asks softly — carefully. He has to be careful with April sometimes, like she's less his friend, and more his sister. When her dad was gone, Casey learned how to steer around certain topics; less stories about how his dad brought home tacos for dinner, more stories about how his dad once lost four teeth in a pro match. Things that weren't too close to home. And when April wanted to go see the zombie film fest instead of the Batman marathon he'd been waiting for months to see, Casey sucked it up. And you don't ask April if she's _okay_. Not about things like this. Because April will give the shitlook, and say _I'm fine_ , _okay?_

But here's the thing: Casey has known April for almost a year, now, and he's seen her lying to Irma enough to know when she'd be lying to him as well.

And here's the other thing: Casey has never met Karai face-to-face. All he's got are stories, mostly from Raph, that started up being like _I would totally punch a girl and it would totally be her, twice, in the face_ and eventually became _We gotta fix this somehow, I guess._

He's never really heard about April's side of things. April sides with the turtles, because that's what she does, but there are times when the turtles talk about poor Karai, brainwashed by her evil psycho fake-daddy, and shadows cloud April's face like a storm on the horizon.

"We need to get Raph home," April says, ignoring Casey's unasked question. Her voice is rough, and her hands are balled into fists, squeezed so tight that her knuckles are white. She breathes harshly, slowly, through her nose once, twice, three times. One of Raph's arm—head—things stirs, the tongue flickering gently along Casey's skin, then twists closer and curves around his wrist. "We need to get them _all_ home."

"Yeah," Casey agrees, carefully peeling Raph away. "I know."

"Come on." She tosses him a handful of his bedsheets. "Karai's waiting for us."

* * *

The less Casey thinks about how they got Raph out of his apartment and back to the lair, the better, but it reminded him too much of hauling a body for comfort, like in the movies his dad watches sometimes. Casey Jones doesn't kill people, he just teaches them a lesson. Raph sulked the whole way down, and if he'd been able to speak Casey's pretty sure he knows what Raph would have been bitching about: _it's cold_ or _people will see us_ or _Casey get off my ass_.

Stretched out, Raph is as long as Casey is tall, and when they finally get him into the Shellraiser, he slides to the back of the truck and won't move again until Casey sits in Mikey's spot and lets Raph wind around his feet.

Karai cranes her neck from Leo's seat up front. "Hey there," she says, all smooth. "You two buckled up?"

Casey narrows his eyes at her and doesn't mention that the only seat in the whole damn truck that has a seatbelt is the jump-seat Donnie installed for April. "Yeah," he snaps. "We're good."

And if Raph is a clingy snuggler, he's also _the actual worst_ to take on a road trip. He hisses at _everything_ — when Karai stops at a red light, when they hit a pothole, when the whole truck jolts as Karai swings them back into the tunnels and onto the tracks. It takes everything Casey has to stop Raph from swinging himself up to the front of the truck when Karai hits the brakes a little too hard, and contents himself with the sympathetic look April shoots him from Donnie's station.

When Karai pulls up alongside the platform, nobody wants to ask the question that needs to be asked: how do they get Raph inside and, more importantly, how do they _keep_ Raph in a big open space like the lair?

"What about Donnie's lab?" Casey asks. "We could keep Raph in there."

April shakes her head. "He keeps the garage door locked," she says. "If what Karai says is true and Splinter's… _food_ , we can't let Raph near Master Splinter."

"So we go into the lab and open it." Karai folds her arms, leaning back against Leo's seat. "I can back the truck in and then we let Raph out into the lab."

"Works for me," Casey says, as April glares.

"Wait," she interrupts. "So we just _leave_ Raph in the truck until we open the door?"

"I don't see you with any better ideas, Princess."

Casey has never seen April look more likely to stab something than he has at that moment, when April whips around, her eyes narrowed and her body arced ready to attack.

(Even at times like these, Casey Jones can appreciate that April at her most violent is April at her most hottest.)

"I _said_ , don't call me that."

Karai doesn't even look bothered.

"We can't just _leave_ Raph here!"

"Red, seriously, it's cool. Raph's gonna be okay, right buddy?" Casey runs his knuckles along Raph's head again. "We'll go out, talk to Splinter, and then we can get Raph here into the lab."

He watches until the tight line of April's spine eases into something a little calmer, less about to scratch Karai's eyes out. "Fine," April snaps, and slams her first against the door release. She stomps out onto the platform.

Karai reaches up and pinches her nose. "Close the door when you're done," she tosses over her shoulder. She doesn't even look at Casey as she leaves.

* * *

Casey has never had a dog.

He'd always imagined himself growing up to get a big jowly hound, more drool than dog, that he could take out to Central Park and wrestle in the dog parks and buy street meat for on the way home. And then he got Raph, who was kind of the same thing, except Raph also understood _talk shit, get hit_ and did it on _purpose_ just for the fun of a fight.

The worst thing about dogs, to Casey, though, is their _eyes_. When they look _sad_ and make you feel _guilty_ because you won't give them the last bite of your cheeseburger, or they shit in your shoe and they're so very sorry, and please don't go to work today, instead please won't you aggressively rub their belly until their foot starts to kick, because you are _the greatest thing in the world_ to them.

Raph has not shit in Casey's shoe. Raph didn't even break Casey's window, and Casey has no food to be guilted out of. But when Casey tries to leave the Shellraiser, Raph slithers forward, his head dropped low. "Sorry, buddy," Casey says, hitting the door release with his fist, and the Shellraiser doors close on Raph with the biggest, saddest pair of murder-eyes Casey has ever seen.

By the time Casey has gotten away from the Shellraiser, feeling like crap, both Karai and April are stopped at the doors to the lab. For one brief moment, Casey wonders if this is his time to shine — _of course_ he can open the door, ladies, because Casey Jones lets nothing stand in his way! — but when he gets to the lab doors and sees the heavy chain wrapped around the door handles, he changes his mind pretty quick.

"Miwa."

As one, the three of them turn around.

From the kitchen, Splinter starts to cross the lair, and Casey clues into it a second before April does: Splinter's leaning too heavily on that cane of his.

"Master Splinter." April covers her mouth with her hands. "Are you okay? What happened—?"

As soon as she finishes that last word, Karai shoves past her. "Father," she says, quiet and worried as she walks right into Splinter's personal space. She looks him up and down, and then her face pulls into a scowl. "You're hurt."

Splinter looks over their heads and to the locked door of Donnie's Nerd Kingdom. "Leonardo has returned home," he says.

* * *

The lab has always been one of April's safe spaces. When she couldn't study at home because of her aunt's sympathetic looks ( _April, honey, I—_ aliens _? Maybe it would help to talk to someone about this_ ), or when the lair was loud and overwhelming, Donnie would set her up with her own side of his desk, and they'd just work, quietly. Even the times when Donnie would sit in the corner playing with mutagen and she just wanted to nap, she'd come here, and Donnie would leave her be, the warm thrill in his mind wrapping around her like an old blanket.

The idea of Donnie's most sacred space being used as a prison for his brothers is _wrong_. Everything about it is _wrong_. As Raph coils out of the Shellraiser and into the lab, the fluorescent lights pick out a run of pale scales in the thick shape of a lighting bolt down his left flank. Slumped into a corner, Leo doesn't move but for the steady rise and fall of his breathing. The side of his head looks swollen and sore, a bruise forming from where Master Splinter must have struck the final blow with his cane.

Instead of approaching his brother, like April expected, Raph rears up and reels away, skimming across the floor until he cowers in the corner next to Timothy's tank.

Something is wrong.

April doesn't need her powers to know that, though she uses them anyway, tapping into the air and listening to everything she can't hear. The air is full of menace, and violence, and fright and fear. "Casey," she says, and he nods, stepping to her side as they watch how Raph trembles and shifts and starts to hiss, watching all of them with something vicious and untamed.

"Okay, it's okay, buddy, I'm not gonna hurt you," Casey says, soft and placating as he creeps closer, but it doesn't work: Raph continues to hiss and spit, venom bubbling a warning in his throat. The air thickens, darkens until every corner is filled with shadows, and even the frozen, miserable gaze from Timothy's tank begins to look baleful and malevolent.

Leo is still asleep, and April can't help herself, she reaches over, running her hand over the welt on Leo's face. Her brow knots, and the room twists further, something reaching out in the darkness towards Raph, towards _her_. "Casey," she says again, her voice catching. Casey straightens up and turns back towards her.

"C'mon, Red," Casey touches her arm gently. "We gotta go talk to Splinter."

* * *

In the kitchen, Splinter sits on a stool as Karai digs through the beaten old first aid kit that lives under the sink. It's a bad bite on his foot, the skin around each puncture wound puffy and weeping. Casey wonders if the snakes are poisonous. He looks over at Red, and just _knows_ , in his gut, that she's got the same worries as him right now. If Splinter goes down to a snake bite, that's messed up, and he doesn't want to be around when the turtles get changed back when that news gets delivered: _hey so Leo guess what you did while you were brainwashed and mutant-crazy_.

"I can go topside," he offers, mentally calculating how much of his allowance he has left in his wallet. "If we need…anything."

Karai looks up, and Casey suddenly feels awkward under her gaze; after all the stories he's been told about Karai, he always expected to meet her in a fight, not chilling in the lair. "I think we're good. The bite was clean."

"Yeah, but like," Casey says, then stops. They're in _the sewers_. No matter how much Mikey always yells about _NEW YORK TUNNELS, YO_ , Casey knows that it's not exactly something they're proud of, that they have to hide away underground dodging turds on their way home. Sometimes, when it rains, and the river gets heavy, there are sandbags around the tire pool just in case, and nobody talks about the last time a hurricane rained itself out over Manhattan. It's dirty, and it stinks, but it's all they've got.

Casey has to be careful. He's just not always _good_ at being careful.

"I think Casey just means, in case we run out," April fills in, leaning against the fridge. Casey feels a rush of gratitude in his chest, but April isn't looking at him. Instead, her arms are folded and she's looking straight at Karai. "Better safe than sorry."

There's a weight behind that last sentence that doesn't sit right.

Splinter doesn't say anything for a long moment, his hand drifting to his long beard, before he makes a soft _mm_ in his chest, and nods. "Very well then."

"Master Splinter," April says, hesitating before she goes all-in with, "what _happened_ out there? Did Leo really—?"

"Leonardo is home," Splinter says. "That is all that matters."

"Dude," Casey says, the full implication hitting him. "Did you lay him out? That's—! …sucks," he adds, changing tack as soon as April and Karai _both_ turn their shitlooks on him and oh shit, if Red's wasn't scary enough, Karai literally looks ready to murder him.

Splinter gets to his feet, testing his weight on his bound foot. "How is Raphael?"

"Asleep. He's in the lab, with Leo," April replies. "I think they're _both_ asleep, I can't— hear anything else." Casey frowns, glancing over at her, but again April isn't looking at him. He'd expected April to say how she _sensed_ Leo and Raph, with that weird Kraang thing she has. As he watches her, April's eyes flick to Karai for half a second, and then Casey gets it.

"I can go take a look," he offers, gallantly.

"No." Splinter shakes his head. "Let them rest. We must find the others."

Casey keeps his mouth shut instead of asking _where do we start?_. Leo came home himself, and Raph came to Casey's. But Donnie didn't go to April's, and Mikey didn't go to Murakami's. The news is full of reports of weird snake sightings, but nobody's reported a capture. He glances at April, casually rubbing her temple under her hair, and waits until he catches her eye.

She nods once.

* * *

"'Kay, so," Casey says, "why don't I just. Wait here, huh? How's that sound?"

"You're seriously telling me that there's some creep called _The Rat King_?" Karai says, like she's trying not to laugh. April bites the inside of her cheek.

"That's what I'm telling you," she says. "He's dead now. And Casey, no. Come on, it'll be fine."

What's left of the Rat King's lair is made up of trashed cables and cages, smashed bricks, and hundreds upon thousands of scuffling, squeaking rats. From where they're standing up on a high bridge, the rats look like a seething, swarming mass, an ocean of fur and disease. Then, like a whale breaking the surface of the sea, a great mouth opens, is filled with unsuspecting, curious rats, and then slams shut.

Casey makes a noise in his throat like he's about to hurl.

The snake burps. One rat makes a desperate, daring escape from its jaws, and then is snatched back by both of the snake's smaller heads. As the rat screams, both heads tug and tear at it, until in a wet shower of blood, the rat is torn apart, and then devoured.

("Your dad's a therapist, right, Red?"

"Psychologist, and come _on_ , Casey, quit goofing around. We need to get Mikey home."

"Yeah, _great idea_ ," Casey hisses, "except he's _kind of busy right now_." )

Mikey looks a little longer than Raph does, from this distance. Longer and heavier, though that might be the ball of rats in his gut. He burps again, then sinks back down beneath the wave of rats.

April rubs at her temple again. Her own emotions are dammed behind a high wall, frothing and boiling and ready to burst. Casey is buffering her, with his reluctance to be where they are coupled with the always barely-leashed bloodlust, his needle-prick of embarrassment and the ice-drop of fear at _so many rats_. Then there's Karai, and the mess that she is, and then, twisted and familiar all at the same time, a bright sweep of a long, languid, contented laziness. "It's okay," April says after a moment. "I think— I think he's just tired."

"Food coma?" Casey asks, then snorts.

Karai looks at where the snake is sprawled out, content and fat and paying no attention to the writhing mass slowly making its way down its gullet. "He's asleep?" she asks.

April nods.

Karai claps her hands against her thighs. "Then we drag him back," she says, jumping down and wading through the rats.

* * *

 **tbc.**


	4. Part 4

tmnt is not mine!

thank you guys for sticking with this story! plot is imminent!

 _in this chapter:_ knock knock.

* * *

 **Birth of Serpents  
part 4**

* * *

It feels like he has not eaten in _days_.

Ever since… his birth? Was he born this hungry? But he remembers snatches of something else — another life? — where his body was not as sleek and he could not slip through the tunnels when people got too close. So maybe he was older than he thought. So, then, not quite a birth but… something. Something _new_ , a renewal, a _re_ birth? The words don't come easily as they should (should they?) — instead, all there is is the gnawing, miserable _hunger_.

He wonders if his brothers (they were his brothers, he knew that much) felt the same. Maybe that was why they dragged their fangs against him when he had found them: they were hungry, they were all so _hungry_ that their jaws ached and their throats worked and saliva pooled in the hollows where their tongues lay.

He had escaped them; slipping through a tunnel and into the water, until he came here, a small run-off, where there were no jaws snapping at him, and his head was empty but for himself, and where there had only been the soft burbling coo of pigeons until he had swallowed them whole.

They had not been enough, and now he he is hurt, and hungry, and the scent of his own blood makes his mouth water. Soon he will have to move again, to find something else to eat, to find something to salve the tears down his flank. Lifting his head, he flicks his tongue out, the forked tip tasting the air and his stomach wrenches at the flavours: there is human, there is filth, there is _rat_. So close, as close as though they are walking straight into his jaws. A ripple of unease works its way down his spine, from heads to tail; when has he ever been this lucky? But he has dim memories of being very small, in another body, and very hungry; dim enough that he can't remember anything except that he needs to eat, and he will not consent to being hungry again.

There are three humans approaching; he can hear them now, two of them he knows, and one of them he _hates_. They stink of the tunnels, and of sweat, and the girl he hates, she _reeks_ , with rat's blood on her hands and on her skin. He could eat _her_ , it would be enough to tear her apart and swallow her down. It would take days to digest her, and the other two would be a bonus, and then he would find the rat she stank of, and eat that, until the wretched twist in his gut was satisfied.

He hunkers low, coiling up in the mouth of the run-off, just out of their sightlines — and waits. Their footsteps splash and echo along the tunnel walls, closer and closer. He lifts himself up, his mouths open, and he readies himself — he wants to rip her apart, and then swallow her down, piece by piece. He _hates_ her. He has been _bred_ for hate. He wants her bleeding around his fangs, to feel her body disintegrating in his gut until she is _nothing_.

If he moves silently, if he moves swiftly, he can snatch her between his jaws before they realise he is here.

But one of the sets of footsteps has disappeared; there are only two when there should be three, and they are ready for a fight — no, no, how did they know he was here? The girl has a sword held high and the one next to her is holding a stick and he doesn't want to fight he wants to _feed_.

He rears up; if he is going to attack, he must strike fast, and if he is going to run, he must run fast.

" _Donnie_."

 _He knows that voice_. She's behind him. He pulls back, all of his weight held high, to look at her, and when he turns all eyes towards her, his heart doesn't have time to twist. He knows her, he loves her, and she shoots him.

Just once.

He can see it with his second and third sets of eyes: a small metal dart, the attached canister empty, embedded in his chest.

The world distorts, and then is nothing.

* * *

"Nice shot."

Instead of replying, April lets her left fist curl up as Karai picks her way through the sludge at their feet towards Donnie. He fell heavily, splattering sewage up and down the tunnel walls, and now he's still. If it weren't for the quiet itch in the back of her head, he could almost pass for dead.

April shivers.

"I wasn't aiming for there," she says, shoving the tranq gun back into her messenger bag. It's empty now, but just to be sure, she makes the safety is on — they don't need her shooting herself in the leg right now.

Karai shrugs, already inspecting Donnie's body. "It did the job," she says. April half-expects Karai to use her feet with Donnie, but instead, Karai is almost… gentle, crouching down and peeling back one of Donnie's eyes to check that yes, he is actually out cold. His brow is twisted up, as though in pain, and April wishes she find something — _anything_ , to know that Donnie was still in there, somewhere. But when she'd been tracking him through the tunnels, it hadn't been _Donnie_ , but the thin, vicious thread of madness that had infested his brothers. And if Leo had been warped enough to attack Splinter, and Raph is now little more than a pet— what does that mean about Donnie?

"Hey," Karai orders, snapping April out of her miserable thoughts. "Jones, get over here."

Casey goes.

"Casey!" April snaps, inwardly wincing at how shrill she sounds. "Karai, you can't just—"

Casey turns, his gaze full of a sympathy that makes April feel sick, and April comes right up against how quickly everything has just _changed_ now — that Karai is here, and now _in charge_ , that Casey is _following her_ , that April is being left out in the cold. Karai is Splinter's daughter, and April is not _his child_ anymore. And _Karai_ is the turtles' _sister_ , and April is just their friend. But Casey was _hers_ , she thinks selfishly. Casey was _April's_ friend, the one who she could talk to about the turtles without worrying about codewords or Irma figuring her big secret out. Casey would see the bruises on her arms and legs and not ask questions about where April goes after school when she disappears in the alley before her block.

Now Casey is standing next to Karai, talking about how they're going to drag Donnie back: do they (can they even?) carry him, or just drag him through sewage and hope that a shower will clean him off at home.

He's not standing by April. He's not on her side. Karai is giving the orders here, and she and Casey have to follow them whether she likes it or not.

"We gotta get him home, Red," Casey says, already crouching to assess Donnie's long, unconscious body. Karai has already pulled the dart out, leaving another thin trickle of blood on Donnie, another thing that he doesn't react to. April closes her eyes, taking in a deep breath through her nose before she nods.

She's being selfish. Donnie needs her.

The turtles need her.

* * *

In the small space of the Shellraiser, the sewage stuck to Donatello stinks worse than the rat blood that had covered Mikey. But the tranquiliser has kept him out, and while Casey and O'Neil see to him, Karai is already planning their next moves.

They have Donatello back now, so that makes four, and that leaves the biggest question still unanswered: _now what_? So they have all four brothers back. So what? That doesn't mean anything if they're still four giant killer snakes, and it doesn't mean anything if it means the Shredder gets to win — he _doesn't_ get to win. Not as far as Karai's concerned. But if Donatello's a snake too, what does that mean for making a retromutagen? What if they can't, now that he's gone?

For a moment, Karai entertains the thought of driving all four snakes to the church, and letting them loose. It'd be worth it. It'd be _deserved_. If Shredder got torn up by the same things he'd created to kill Karai's father — that'd be _fair_.

Because Shredder deserves to _die_. He deserves a lonely, painful death like the one her mother had; a _miserable_ death like the one he planned for Splinter, and he deserves to be ripped apart the way he wanted to rip apart the turtles. And the rest of his honourless underlings — Bradford, Tiger Claw — they all deserved to die as well. Karai would raze the whole clan, then set the wreckage on fire and then light incense for her mother with the flames.

...but Karai's not the only person who wants Shredder gone. Somewhere, deep down in each one of the turtles, she's pretty sure they want to watch Shredder suffer just as much as she does, and what better way to twist the knife into Oroku Saki's gut than for him to watch all six of them take him down, _together_?

She tightens her hands around the steering wheel until she can feel her nails against her palms, but forces herself to relax. She needs to be controlled. She needs to be ready. She needs a plan.

"I don't know what to tell Sensei," O'Neil says quietly. Karai flicks her eyes up to the mirror; O'Neil's shifted, not in her seat anymore but on the floor, Donatello's head in her lap, and leaning against Casey's side. As they talk quietly, he winds his arm around her shoulders, and Karai strains to listen to them both.

"Tell Sensei what?" Casey asks.

April reaches out, her finger tracing the air over one long bloody rip. "One of the others did that to him. They must have fought."

"We don't know that." Casey pulls her hand into his, away from the oozing wounds, and folds his fingers around hers. "It coulda been something else."

Karai shuts her mouth before she interrupts. It could have been, but she has a horrible feeling that O'Neil is right.

* * *

"My son," Splinter said, in a horrible, quiet tone of devastation, when they finally hauled Donnie into the lair. They cleaned out his wounds, wrapped torn strips of bedsheets around his flank, then pulled him into the lab, and he slept through it all. There, they left him in the corner opposite Raph, who immediately tried to wind himself around Casey again and then given him _The Eyes_ when Casey had pushed him away.

"You know," he snaps at April when they finally get out of the lab, and Raph sadly, gently, headbutts the door in three-part harmony. "why couldn't _Donnie_ have been the cuddle-buddy? At least you'd enjoy it."

Karai smirks. She looks dangerous in the dim lighting, her bright red lips curving into something wicked and sharp that catches his eye in the brief moment before April snarls, "Shut up." Casey does, raising his hands in defence as she goes on: "We need to figure out what our next moves are."

"Already working on it," Karai replies, before Casey can agree.

"And are you going to share those plans with the rest of us?" April asks, folding her arms. Casey knows that stance, and (wisely, he thinks) chooses to keep his mouth shut. That's April's asshole voice; it's how April talks to Leo when Leo's being a real jerk, or how she talks to people at school when she thinks they're dumber than a bag of rocks. It's how she used to talk to Casey, once.

Karai doesn't even look April's way. "Maybe. I'm not finished yet. It's not like I have a ton to work with."

"What is _that_ supposed to mean?"

"Seriously? We're probably going to have to take on the Foot at some point. Father can't fight with his foot like that. So I've got a so-called vigilante—"

" _So-called_!?" Casey yelps reflexively. "I'm not _so-called_! You think these streets would be any safer without _me_ around?"

Karai rolls her eyes, and makes it look she's dealing with a very angry, very stupid three-year-old. "Great, so you beat up the Purple Dragons. What else do you do, steal their lunch money?"

"Yeah, actually," Casey shoots back, disgusted. He's not some cheap thief, never has been, and as tempting as it is sometimes to rinse the Purple Dragons for every last sticky cent in their pockets, ultimately, he'd only be stealing money that _they already stole_. Even though the Purple Dragons owe him like, ten new bats, he's not taking what used to be some nice old lady's savings to pay for them. He sneers at Karai. "And then I throw a pizza party with it. What do you take me for?"

" _One so-called vigilante_ ," Karai says, raising her voice, "one alien target, and me. Against _the Foot Clan_."

"We've been handling the Foot!" Casey gets to his feet, feeling small under Karai's dismissal. "We were handling you and the Kraang and everyone else _just fine_."

"No, _the turtles_ were," Karai says.

She has a point, but. "And everything they couldn't do, who do you think was doing it?" He jerks a thumb at himself. " _Casey Jones_!"

"Casey, stop. She's right," April looks up from her fortress of notebooks that she grabbed on each trip into and out of the lab. "We're not the turtles. But that doesn't mean we're _useless_." She aims this last shot at Karai, who doesn't react. "We can help."

"I _know_ you can help," Karai says, eventually. "I just how to figure out _how_ you can help."

"I have Donnie's notes." April pats the stack of books next to her. "And his computer's still in the kitchen. Maybe there's something we can use."

"Good idea," Karai says. April blinks, looking surprised. "You get whatever you can from that, I'm going to talk to Father."

Before anybody can make a comment on _who died and made you leader_ — and Casey thinks that it's probably for the best (Leo's not dead, he's just psycho and mutated and that's totally not the same thing, right?), she turns smoothly on her heel, and heads up to the dojo.

Casey congratulates himself for staring at her ass for less than two seconds, and reminds himself that her attitude aside, Karai is kind of crazy, and there is exactly one rule about crazy and its relationship to his dick. He flops down next to April, leaning his elbow on the bulge of the beanbag. "So what do we got?"

April shoots him a look under her bangs — it's _almost_ sly, and he finds himself grinning in response, his heart thumping a little faster. "Homework," April says. She sets a notebook aside and Casey picks it up, his arms twitching with the need to do _something_ : Casey Jones doesn't do well doing nothing. And Casey knows his way around a couple of machines, so if they find some kind of blueprint, he's pretty sure he can at least try to build it.

This notebook is not one of Donnie's engineering wonderbooks, though. Casey can recognise numbers, and like, three symbols he picked up in swing-set trig class. The rest is even worse than a whole thing written in a foreign language — at least then he'd have a legitimate reason to be useless. Instead, Donnie's notes are full of half-letters and words that should make sense and don't, because once upon a time, the words on Donnie's pages were English, until Donnie got a hold of them along with the rest of the 'scientific community' and decided to throw it all in a blender.

"Dude," Casey says, despite himself. "What even _is_ this? It's like, half science, half math, all nerd."

"It's his retromutagen formulas," April replies, her voice distant and soft. "The one he made for my dad."

Casey bites back a joke about Donnie needing a translator's note, and settles next to her, peeling a fresh notebook off the pile and cracking it open. Donnie's handwriting changes depending on the page: sometimes it's painstakingly perfect, detailing chemical formulas and equations, and others it's scrawl, where Donnie has tried to work out some form of his Einstein-level math using a kid's colouring pen. Every few pages there's half-drawn sketches, too: one of Metalhead's head, one stick-figure drawing of Donnie strangling Mikey, one of Neil deGrasse Tyson in a macho-man pose busting out of his shirt and punching what looks like Chuck Norris.

Across the room, Raph gently butts the door again.

Casey lets his gaze drift to the big blue box next to the lab door. Big, blocky marker letters spell out RAPH DO NOT SHOOT MIKEY along the side (and then _sensei please shoot Mikey_ in someone else's handwriting underneath). It's so tempting to just put Raph out, and keep putting him out until this whole thing is over. Put them _all_ out. Let them all sleep it off and maybe when they wake up, Casey can lie to them about how this whole thing was just a really bad dream.

It's cool and all that Donnie somehow had a stockpile of weapons-grade tranquilisers hidden away in his Nerd Palace, but the whole idea makes him _really glad_ Donnie's one of the _good guys_ , because one day they'll be talking about the next cool thing to do, and someone will say _gee, some C4 would be pretty great right about now_ , and then Donnie will smile, go " _aaaah_!" while doing his Scientist Finger In The Air thing, and ten minutes later they'll be wanted felons.

If it wasn't for Donnie not knowing when he was _beat_ when it came to April, he could almost, _almost_ , be cool as hell.

"So we make a retromutagen," he says, looking over April's shoulder again. "No big. We can get the stuff, right?"

"Right." April chews her lip. "It's just— getting it— Donnie—" She pauses, swallows, and when she talks again, her voice sounds choked. "We need a lot," she says instead, and as she speaks, her voice ramps up. "My dad could have been a fluke. They might need the whole thing — each. And they're _already mutants_ , Casey. How do you retromutate a _mutant_? What if it goes wrong and we just turn them back into turtles?"

He doesn't know, because now she's mentioned it, he's thinking the same thing. How _do_ you unmutate a mutant, but only half-way? What if they turn into little tiny tank turts again? What if they get twisted even worse, into cheap B-movie monster versions of what they are now — snake-mouths and turtle bodies and snake heads for hands? What if it just doesn't work, and they stay as snakes forever — or what if they melt into goop, like the monster in Donnie's lab?

" _What if I don't see them again_?" April says, her voice breaking into a high squeak, and she crumples forward, her hands cupping her nose and mouth as though magically all her crying will hide in there where nobody else can see it.

Way back when April came to the rink that time — Casey can see it now for what he had hoped it wasn't — she literally had no place else to go. Irma would have gotten snotty and asked snotty questions, he'd never really seen her close to anybody else at school, and the turtles were the reason she was so lonely. Her dad was a bat, she had no mom, no friends, and her aunt wasn't exactly the understanding type. Casey was all she had. So he knows what to do, now that he knows April better.

"Hey, c'mere," he says, sliding his arm around her again. April is small, and skinny, and she fits right in when she lets herself. "We're gonna fix this." She slumps against him, and he takes the opportunity to rest his chin in her hair. She smells of shampoo and sewer and sweat, and every time her body shakes, her hair scratches up against his face. "It's gonna be okay, I promise."

April shakes her head in three angry shakes — Casey can't promise, not this — so he tells her again: " _I promise_."

* * *

"I spoke with Father," Karai says, appearing at the edge of the pit.

"How's his foot?" April asks immediately, throwing Casey's arm from around her shoulder. Her nose still feels damp underneath, but wiping it away would make it more obvious that she was crying than leaving it would be.

The thin flicker of uncertainty in Karai is ice cold, but Karai doesn't say anything except for "he's sleeping", which _isn't an answer_. April opens her mouth to tell Karai exactly that, but Karai overrides her, dropping onto a cushion at Casey's side, her legs crossed. She leans forward. "We came up with some options."

"Great," April says. " _How's his foot_?"

"He's _sleeping_ ," Karai says again, evasive. "I don't think he slept last night."

April pushes: "But the bite was clean, right?"

"What I _saw_ was clean."

April sits back, unpleasantly satisfied, and a tiny grain of horror sticks in her heart. So Splinter might be slowly dying thanks to the venom in the bite. At least now she knows, and Casey knows. That means they have another deadline: they need an anti-venom. She glances to Casey, who is already scowling, his jaw set and determined. But they can't take Splinter to the hospital for a check-over, and every time April gets the quiet little idea of checking WebVet, guilt rises up and chokes her. Master Splinter might be a rat, but he's also _not a rat_.

"So." Karai leans forward, spreading a piece of paper out. "There are our options."

There are a lot of them, ranging from the deceptively simple (make their own retromutagen), to the incredibly dangerous (infiltrating Kraang laboratories). Karai talks through each one in turn, but she doesn't speak with the quiet determination that Leo has after he's spoken with Splinter; the reassurance that he's going to do a good job — instead, Karai _isn't_ sure, and April can feel it. It shudders through both of them every time Karai comes to a particularly dangerous plan, and each time there's the slow, mournful _thump-thump-thump_ of snake on steel. "We really need to get your boyfriend a hobby, Jones," Karai says smoothly at one point, and Casey just as smoothly flips her off.

April ignores the slight, focusing on Karai's ideas, and her tight neat handwriting. There's a knot in her that's determined to find any and every flaw in Karai's plans — because this isn't just about Karai, walking in like she owns the place, and how two weeks ago Karai was dancing around Leo's heart and trying to lead him up to Shredder's door. It's not the fact that April can't trust her. It's about the turtles, and how they can't afford to make even the slightest mistake.

"Okay, you know what?" Karai snaps, when April points out yet another flaw. "You might not like me, but this is not my fault, and I _am_ going to stick around and see this through. So you can either work with me here, or find a door and walk out of it."

"I was here _first_ ," April forces herself not to yell; instead, her voice comes out rough with anger. "I was here when you were trying to kill them, and so was Casey. So we're not leaving and you're _not_ going to boss us around. That idea is going to get us _killed_."

"Well maybe if the _turtles_ had a few more _friends_ that we could call on then this wouldn't be such a problem."

April opens her mouth to object — _of course the turtles have friends_ — and then shuts it. They really don't. Aside from the kid who likes to LARP, and Leatherhead, who's all but gone, the turtles don't have anything in the city other than enemies. There's Slash, at a push, but even the thought of hunting Slash down to call in a favour sends shivers down April's spine. Kurtzman, maybe. Everyone else wants to at least hurt them, if not worse.

"It's not their fault everybody wants them dead," she shoots back instead, but even that's not true, either. She doesn't even know how many other people were affected by the mutagen spill — all she knows is how many people Donnie has managed to cure: just one.

The lab door rattles once, as though an aggrieved turtle wants to defend himself, then something slides up against it. There's another _thump_ , and then another, and then another, and April bites the inside of her cheek as something gives a quiet, mournful hiss.

* * *

Karai sighs as the thumping gets more and more erratic. "Okay, seriously?"

Casey makes a long, tired noise in his throat. "It's _Raph_ ," he says, then adds, "probably."

April looks half-sympathetic, for like, a second. Then she turns right back to Karai and the two of them start yelling again.

Any other time — literally, _any other time_ — Casey could appreciate the idea of two kunoichi about to throw down in front of him. He'd probably get popcorn. But right now, he really doesn't want to watch them beat the snot out of each other when they have four killer snakes in the room next door.

Casey plays hockey. Sometimes things get heavy, and sometimes the wrong punches are thrown, and sometimes you need a decoy before things get really nasty.

" _Knock it off_!" he yells.

Both of them turn to look at him, and Casey understands how zebra feel right before they get torn up on nature shows. He holds up his hands in a useless gesture of peace. "I'm just sayin'," he says, offering his best smile. "Yelling isn't gonna help anybody."

Karai snots at him, then turns back to April. April's already got her game-face back on, her brows pulled together and her hands curled at her sides — Karai just needs to say one more wrong thing, and April will charge.

The look on Karai's face reminds Casey so much of Leo — half full of pity and half full of disdain — that he almost points it out, but again remembers that he _likes being alive_. It's the same look Leo gives Raph just before he says something smug that sets Raph off into one of his _you don't understand me_ sulks, and Leo rolls his eyes and sighs dramatically because _yes, Raph, we all understand you, you're being a brat_ , and maybe if Leo wasn't such a _snot_ , Raph wouldn't want to punch him so hard all the time, and—

Karai opens her mouth to speak—

 _Slam_.

All eyes turn towards the lab.

Something slams against the door again, heavier, like one of the turtles has hurled himself bodily at the doors. Then something starts to pull, rattling the locked doors as though trying to find someway for them to give out. The padlock Splinter set on the chains clonks heavily against the metal, ringing dully.

Casey turns on his heel, throwing his bandana against the couch: " _Raph, quit it_!"

The rattling at the door falls silent.

Then the hissing starts. "Raph!" Casey snaps again, imagining Raph's big sad eyes and immediately feeling guilty — considering it's _Raph_ , there are worse things he could be doing as a Giant Killer Snake than wanting hugs.

April makes a mournful sound.

Casey can feel his stomach knot, even as he turns around to see that April has her hand to her temple. _Aw crap_ , he thinks, because whenever April does that, bad stuff seems to happen, and sure enough, April goes and opens her mouth. "Casey, that— that's not Raph," she manages to say, before the sound of scales shifting drags along the door.

Something knocks, politely.

" _Sisster_."

Nobody moves.

"Sisster," the voice says again, as something slowly, languidly presses up against the heavy metal doors of the lab. " _Sisster._ "

Casey clears his throat twice; first to clear the lump, second to make sure that he's not going to squeak all over the lair. "What the hell is that?" he asks.

April meets his gaze, looking about as spooked as he feels, and together they look at Karai. "I think that's for you," April says. She says it like she's trying to be a smart-ass, but Casey can hear it even if Karai can't: April is _freaked out_. He shuffles an inch closer to her. Which would be better right now? His baseball bat, or his hockey stick? The hockey stick worked on Raph, but Leo's different — it's better to smash him fast before he gets the time to get all tactical.

Baseball it is.

With his taser, just for luck.

Karai doesn't say anything, just gets to her feet, all long and lethal, and heads over to the door. Casey tightens his grip on his baseball bat, dropping into a ready stance until he can feel his thighs stretch. April twists to his right, her metal fan flaring out.

"We're good," Casey says, giving Karai the nod. She draws her sword, and holds it in her right hand as she unlocks the door.

Karai opens the door just enough to look, bracing her weight against it in case anything tries to force its way through.

Nothing does.

Leo's just _standing there_. Just regular, turtle Leo.

With bright green eyes, and sharp, sharp teeth.

* * *

 **tbc.**

all comments/crits are loved and adored - thank you guys again for reading this!


	5. Part 5

tmnt is property of viacom.

thank you so much for the comments and feedback! sorry for the delay!

 _in this chapter:_ the team needs a leader.

* * *

 **Birth of Serpents  
part 5**

* * *

As Leo steps out of the lab, Karai closes the door behind him, and locks it.

Karai has always prided herself on being able to read her opponent. Know your enemy, know your ally, know their every move — the ones they just made, and the ones they're going to make. The problem is, she doesn't know Leo — not like this. As Leo walks forward, his shoulders are looser, and his feet tread differently: toe-first and sliding to heel, instead of heel-first. And this is Leo's _home_ , but he looks around the lair with an assessing eye, mapping out corners and crevices, the way Karai does herself when she finds a new battleground.

Something's not right.

As Leo moves forward, she follows him, focusing on his _ki_ , and his posture, everything that makes him _Leo_. He's too smooth, too elegant, and in the sharp lines and edges of his body, all of Leo's smug self-assurance is gone — Leo used to know that he was good, and he wanted _everybody_ to know how good he was. Leo is one of the worst show-offs Karai's ever met.

Now, Leo walks normally, straight shoulders and shell, not looking for anybody's reassurance or approval — because he hasn't even considered that he would need it. Leo's not just _off_. Leo's _gone_.

What's more, she was expecting some sort of reaction from O'Neil — a hug or something, but instead, O'Neil is hanging back, and when Karai looks at her from the corner of her eye, she can see O'Neil sliding into a slight, but obvious, attack posture.

She files that away for now — there are so many things she doesn't know about April O'Neil that aren't being shared, but this is the most pressing: how she knew it wasn't Raph behind the door, and why she's not excited to see Leo now.

But that needs to wait.

"How are you feeling, Leo?" Karai asks instead.

Leo cocks his head. "Okay, I guess." There's none of the snake in his voice now; a small lisp of the _ss_ , maybe, but he doesn't rasp his words, like the voice from before. He sounds close to normal, even. He runs a tongue over his sharp new teeth, then blinks. "Huh," he says, doing it again. His fangs are long, and sharp, and pale in the dim light. "That's new."

"Yeah," Casey drawls, still hanging back, and holding what looks like a potato masher in his left hand. "You should take a look in the mirror."

"You hungry?" Karai asks, letting her posture sink into something slightly casual, her hand on her hip, closest to her pocket full of kunai.

Leo's eyes focus back on her, the snake-pupils narrowing. "Yeah," he says slowly, rolling the word around his mouth. "Hungry."

It takes Karai exactly half a second to come up with a plan, to see just how much of Leo is left. "Hey, O'Neil," Karai says. "Leo's hungry. Go get him something."

Karai can count every single retort that goes through O'Neil's head — _the kitchen's right there_ , and, _this is his house_ , and, _don't tell me what to do_ — before she gets it. She knows.

Maybe this won't be as difficult as Karai thought.

"Okay," O'Neil says, turning and making her way to the kitchen, and the steps to the dojo.

Leo doesn't watch her go; instead, he keeps his eyes fixed on Karai, and not in any way she'd like. "What happened?" he asks. "Why are my teeth—" He gestures to his mouth. "…Y'know?"

"What do you remember?" Karai asks him back.

Leo pulls a face. "Not much. There was a fight?" It's more of a question than a statement, and he watches Karai as she nods. "Oh," he says. "Shredder?"

"Yeah."

He doesn't ask about his brothers, and Karai's not good at small-talk. Behind her, Casey shifts awkwardly, the slow _whoop_ of him spinning his baseball bat between his fingers the only other sound until they can hear soft voices from the dojo, and O'Neil reappears at the top of the stairs. She's not alone. "Leonardo," Splinter says, a note of relief in his voice as he limps down the stairs behind her. "How are you feeling?"

"Good, I think," Leo says, turning to face Splinter. "And—"

He stops talking. His nostrils flare, and they all notice the tightening of Leo's muscles in the split-second before he lunges.

It happens mid-air, in slow-motion. Leo's body shifts to become lither, more serpentine. His face warps and his jaw unhinges, and before any of them manage to shout out a warning, Splinter pushes O'Neil out of the way and into the kitchen before bringing his cane up.

Leo's jaws snap around the wooden staff, and he rolls when Splinter shoves him back by the mouth, rocking over his shell and up into a low crouch. The air crackles with danger, and as he springs into a new attack, Splinter steps to the side, punching Leo in the side of the head — not enough to hurt but enough to unbalance.

The warrior in Karai notices everything — the parts of Splinter's form that are similar to her own teachings and the parts that aren't; the moves that he's had to adapt to his rat form, and the new pressure points he uses on his son, because Leo isn't human and never has been. Most of all, she notices how much Splinter is holding back, compared to Leo.

Leo is not holding back. His strikes are made with all of his weight behind them; he wants to hurt Splinter, but more importantly he wants to incapacitate him, so he's an easy meal. The thought twists Karai's stomach and makes her wrists itch with the need to fight, but she knows the rules: wait until needed, instead of stepping in and making things worse. She whips an arm out as Casey steps forward. "Don't," she warns. "Wait."

When Splinter hesitates as a kick from his son hits too close to the wound on his foot, Karai acts. She moves her hand, and sends a flare of kunai to stab the ground in front of Leo's feet.

He stops, green eyes narrowing as he turns slowly, his bare heels grinding into the concrete.

Karai can feel her own heartbeat, and the crawl of sweat beneath her short hair, and Casey's breath along her shoulder, and Leo's gaze upon her.

"Go," she says.

She uses Casey as a decoy — as he runs in swinging, she slips behind him; he's bigger than her, and wider — he's the perfect target for Leo. Casey yells something ridiculous, and then is cut off as Leo plants a foot in his stomach in a high kick, sending Casey arcing across the lair before he slams into the tyre swing, snapping it from its supports and splashing into the pool. In Casey's wake, she ducks under another of Leo's kicks and sends a kick of her own towards his knees. Once she would have aimed for his jaw, to knock him off balance, and to shut him up, but Leo's mouth is more dangerous now that he's not whining at her to _find the good in you, Karai! I know it's there!_.

Instead, he's silent, and Karai knows that she needs to avoid Leo's mouth, and avoid Leo's hands.

She aims for his gut, and the vulnerable parts left over — his thighs, and his feet, and the soft shell at his sides, and when he sends one set of jaws her way, she reaches for the short sword at her back, intending to parry it away and slice the tendon.

But Splinter yells out, "No!", and instead she drops low, hooking her leg around his knee and pulling it out from underneath him. His shell hits the concrete with a loud _clack_ , and she twists away.

O'Neil is still pinned by the dojo stairs, but her shrill voice rises above Leo's panting: " _Casey! Casey, get the box_!"

Casey runs, hauling himself out of the pool and crossing the lair. Leo twists on the spot, looking wildly between all four of his opponents: Casey, dragging the blue box away from the lab door; O'Neil, wringing her hands around her tessen and obeying her sensei; Karai, waiting for his next move; and then Splinter, favouring the wrong leg and on the defensive. His green eyes move from person to person, and Karai realises what's wrong: Leo can't focus. There are too many opponents, too many enemies.

When Leo gets back to his feet, he hisses, venom frothing in the back of his throat before it arcs through the air and splashes on the floor at O'Neil's feet, stinking and lurid yellow.

The corner of Leo's mouth foams the more frantic he gets, and he slides to the left when Splinter lifts his cane and twists his wrist, spinning it like a bo staff before bringing it down. Leo dislocates an arm to avoid the blow, then shakes it back into place with a thick _slock_.

The smaller snake-heads warp back into fists; Leo blocks and parries and punches, the moves blurring until Karai throws a shuriken past his ear and he starts, the distraction giving Splinter enough time to reach out and pull Leo into _seoi nage_.

Leo backflips away from it, barely steadying himself back on his feet before lunging again, and this time, Splinter is ready for him; Karai's father sidesteps, waiting for the split-second of Leo reorienting himself, before slamming the length of his cane down against the back of Leo's neck.

Leo staggers, a hissed rasp of pain coming out of his mouth, and Splinter presses his weight into the cane until Leo's knees buckle. " _Rat_ ," Leo snarls. His skin bubbles, and his legs start to melt together.

"Jones, _now_!" Karai orders.

The tranq dart embeds itself in the meat of Leo's shoulder, the impact louder than the gunshot itself. Leo stares at it, his hand twisting as he tries to reach for it. "Karai?" he asks, his voice quiet and far-away. His straining joints buckle, and he slides slowly to the ground, and there's the final proof that Leo is not what he should be — he falls _gracefully_ , lithe and smooth, instead of a beaten, defeated teenager.

When the lights go out, he slowly leans forward until his head touches the ground, and lets out a long breath as his body reforms. Then, he does nothing but sleep.

Casey tilts the gun up to his mouth, and blows the barrel.

* * *

When they drag Leo back into the lab, he's not the only one who's shifted.

"Mikey?" April says. It kills Casey to hear the tiny note of hope in her voice, especially when it dies. Mikey doesn't move. Mikey just keeps staring ahead, his green eyes locked on them, and his normally goofy face is cold. Casey wonders what April can feel from all of them — she knew that Leo was crazy before Leo even opened his mouth, but Mikey?

What does that mean about Raph? Raph, the turtle-shaped _definition_ of _dude, no homo_ , should be up and ready for punching — not whining for hugs. What does that mean about _Mikey_ , if April can feel whatever's going on in his head, and it's enough to make her _give up_ before he's even said a word?

Uncomfortable, Casey lets his gaze shift to the dark, shadowy corners of the lab, where Raph and Donnie are hiding: Raph has wound himself around Donnie, and is watching — now that they're all together, Casey can see the differences: Raph is fatter, shorter than Donnie, with the long lightning bolt picked out down his left side. Donnie is long and skinny and bruised, and even in sleep he just looks _sad_.

"Okay," Karai says, dusting her hands off over in the corner where they're leaving Leo — the other side of the lab from Raph and Donnie, Casey notes, but just far enough away from Mikey that neither of them are touching. "Let's go."

"But—" April starts, then scrunches up her face as she nods. Casey doesn't miss the soft, miserable look she sends in Donnie's direction as they leave, and when Karai slides the door shut, he knows they all feel just about as crappy as each-other. But what can they do? It's not like they can just send them to their rooms, all like _time out_ , _you're grounded_.

" _Now_ ," Karai prompts them; she's already back by the door. _Ninjas_ , Casey thinks, almost ruefully. He was used to Raph pulling the whole _one-with-the-shadows_ thing, but he hadn't counted on Karai being able to do it too. "We need to lock them in."

* * *

In the dojo, Splinter flattens his ears against the voices outside as they shut Leonardo back into his cell; meditation is all he can do, to school his thoughts away from the knowledge that the sight of rat, the _stink_ of rat, is enough to rob his sons of the little senses they have left.

It was cruel enough that his sons became his predators, but something even crueler is now in play — that he cannot even care for them when they are hurt. Instead, he has to suffer the indignity of charity, and content himself to be thankful that his daughter has come home, as well as the friends his sons managed to make.

He is lighting another stick of incense, to soothe his own senses and confuse his sons', when Miwa enters the dojo. Her steps are silent, but the crush of the rug underfoot gives her away. "You were losing. Why did you try to stop me from attacking him?" she asks.

He sighs. How does he tell his daughter that he did not want her to attack her brother any more than she had to? That they have fought enough? Let him be the disciplinarian, let Miwa find her place in her family. Instead, he chooses not to answer, and lets his silence speak for him.

"Father," she prompts, impatient. "We don't have a lot of time. If they're-"

"No," he agrees, settling back onto his haunches. "We do not have time. Have you agreed on a plan?"

"Yeah, I _have_ ," she replies, lightning quick. "We need to put it to work. Tell the others they're working for me and we can go out and fix this."

It is exactly what he hoped she wouldn't say.

Miwa has _several_ plans, with sound strategy, but she has no _team_.

Leonardo leads his brothers, and took the role willingly — but Miwa has no role yet. She is as good a ninja as his sons, perhaps better in some respects, even if the forms she uses are not the ones he would have taught her, but she does not have the respect of her peers. April will not trust her, and Casey himself cannot be trusted, too distracted by the promise of battle and bloodlust to be relied upon on a mission. His sons, for all that they were irreverent, and arrogant in their youth, loved each-other and respected each-other's strengths, and had _discipline_.

Miwa has spent too long in command, and in charge — her plans are good, but they are the ideas of a general; they demand respect and deference, and perhaps in the Foot Clan, she had earned that respect, and the position she carried, but equally, here, she has earned nothing but distrust.

In the time it takes for him to think this, Miwa has become impatient. "Don't you want them _back_?" she snaps, throwing a hand to the side. "Don't you want _revenge_ for this!?"

Splinter has _always_ wanted revenge. Deep in the core of him, he has always wanted _justice_ ; Oroku Saki had murdered his wife and, he had thought, his infant daughter. Oroku Saki had forced him out of his homeland, to _America_ of all places, and it had ultimately been because of Oroku Saki that Splinter became _this_.

It is Oroku Saki's fault that his sons are what they are now.

But it was also true that had it not been for Oroku Saki, he would never have had his sons in the first place. Though their life together has been a hard one, with fear and paranoia for bedtime stories instead of fairy tales, he has been blessed, and instead of a long, lonely life as a widower, he has become a father again.

There are, of course, times that he has wondered.

If he had been a better brother, if he had listened to Oroku Saki's grievances about his family, and if he had taken the time to sit with his brother, mediate between him and their father, about _why_ the Foot Clan deserved to be razed to the ground… but he could not be expected to sit and baby-step his brother through this. There were things that his brother should have been expected to _understand_. He should have been _grateful_ — it could have been so easy for his father to have snuffed out the Foot Clan once and for all, instead of giving the last of its line a chance at a better, worthier life.

"Revenge is not the word I would use," he says instead. In truth, it's simply the word he refuses to use. His daughter is too quick to seize on ideals of vengeance, he has realised — always for her mother, and now for her brothers. "First we must focus on our _family_."

Instead of arguing further, Miwa huffs and turns her head aside, and out of the corner of his eye he can see her scowl. "How bad is the venom?" she asks. "I know that's not a normal bite."

"It is purging," he says, after a pause, before giving in to the temptation to share with his daughter a little more of her heritage, moving across the dojo to the small hiding space where the scrolls are kept hidden, safe from inquisitive sons and meddlesome fingers.

"My—" She catches herself. That word is another habit that she needs to break. "The Shredder told me these had burned in the fire," she says instead, running her fingers gently over the worn paper. Good, he thinks — she is treating them with the respect they deserve. "Is it working?"

"It is working enough." It is a strong venom that Leonardo possesses, but Splinter is a stronger ninja. The wound itself is more trouble — Splinter can purge poisons, and wish away aches and sprains, but he cannot knit together torn flesh or heal a broken bone. "Perhaps when this is over, I can teach you."

He does not miss the hungry glint in Miwa's eyes when she asks, "Did you teach my mother?"

"Yes."

"Was _she_ a good healer?"

He is tempted to lie for a brief moment; he wants nothing more for Miwa than to think only the very best of her mother, that Tang Shen could turn her hand to anything and become an expert, that she was the greatest dancer, the best cook, the strongest warrior, but none of these lies could come close to just what kind of a woman his wife really was.

"No," he replies truthfully, thinking of the picture he gave to Miwa, where Tang Shen is quiet and sly and not looking his way. "She was a menace who once turned a bruise into blood poisoning. But perhaps that too was a talent she could have developed, if she had had time."

If his wife and his daughter had had time _together_ , he adds, to himself. But they did not, but they did not, and it is Splinter's private shame that now he must mourn who Miwa _could_ have been.

* * *

"So, uh," Casey makes a vague gesture towards the lab. "I'm guessing nobody's thought about how we're gonna feed them, right?"

April shakes her head, setting one of Donnie's books back down. "Somehow I don't think they're into pizza."

Casey huffs a small laugh through his nose. April sassing is April not close to crying, so he takes the win for what it is and flops down next to her, punching the sides of Raph's beaten old beanbag until it fits him. "I dunno," he says easily, "maybe that's our in. Like a trade — two slices of pepperoni equals _please don't eat your dad for like, two hours_." He picks up another book, ruffling the pages with his thumb before giving up and setting it back down — more math, that only Donnie seems to understand. " _Dear Donnie_ ," he adds, pitching his voice high. " _I will give you two broken scooters if—_ "

"Hey." Karai's voice cuts across the lair.

He tilts his head backwards, until the upside-down image of Karai comes into focus. She marches across the lair, her booted feet clacking on the concrete, and he ticks off a lazy salute before turning back to the TV. It's been on since they locked the lab doors again, the volume kept low in case anything — or any _one_ — changed.

Nobody has. Even Raph's been quiet. The last Casey saw of him was his big sad eyes as they locked the doors, curled around Donnie and far away from Leo.

Leo, the psycho.

Casey screws up his brow and forces his anger to bank itself. This stinks, this _sucks_ , this _bites_ , this is the worst, _shittiest_ thing that has happened to Casey in a long, long time, but right here isn't when he needs to get angry. Not next to April. She's got enough to deal with.

He grabs the remote and starts channel-surfing, looking for any kind of distraction, and shifting as Karai sits on the floor next to him, small ankles crossed at Casey's left. She doesn't say anything, but Casey catches her face darken when he lands on the evening news.

It hasn't even been a _day_.

She glances over to the lab. "How are they doing?" she asks.

April snorts quietly — it's a dumb question, he can't blame her — but Casey answers Karai before April can: "Probably hungry. Mikey's the only one we know ate something."

Karai pulls a face. "Is there a pet store nearby?"

"Yeah," April says, glancing up. "There's one a block up from my apartment. I think they have lizards. I mean, they're not snakes, but we can probably ask."

"I can do it," Casey offers, easing back up to his feet, anything to just move. "I was goin' up there anyway." Which — he was; the whole plan to restock the medkits is still in play, but what Casey doesn't say is that the idea of going topside, and getting out of the lair, makes his brain itch. He needs to _go_.

"I'll come with," Karai says. Casey doesn't miss the flash of suspicion coming from April. Neither does Karai, and she talks before April can: "I think you should stay here, O'Neil. If one of the others changes, they might want a more familiar face."

April shuts her mouth, eyes darting immediately back to the door as she fills in the same gap Casey does: a face that isn't, and never has been, an enemy. She nods once.

* * *

It's that kind of warm New York evening where the air smells of tarmac and dust, and as they move out of the alley and into the sunlight, Casey takes a long, deep breath. He'll never say it, but he doesn't envy Raph. Secret lair or no secret lair, Raph's never sat on a stoop eating a hotdog, or gotten free cookies from nice old Mrs. Horowitz on Purim, or played street hockey with a Coke can and some rollerblades. Casey wouldn't give up the city for anything.

"Pet store's a block this way," he says, tilting his head to the left.

"Actually," Karai says, then looks uncomfortably across the street to a clothes store. It's the fact that she's _uncomfortable_ that gets all of Casey's attention, and he follows to where she's looking — some kind of Hot Topic rip-off that Casey went to once when they sold a band shirt he liked, and then never went back to when they went mainstream and started selling _Twilight_ shirts. "I want to go here first." She picks at her clothes — she left the armour at the lair, but even without that, she's still dressed all in black, and her make-up's gone. In natural light, without the bad-girl eyeliner and caked-on foundation, she looks almost _normal_ , like a girl he'd meet at a show sometime and probably ask out.

But yeah, Casey thinks, he gets it. The clothes she's wearing make her look like she just walked out of a creepy shadow-puppet show, and it's not like she can just go up to Shredder to ask for her clothes back.

He shifts.

"Uh, you need anything?" he asks, twisting his wallet chain around his thumb, and tries not to feel relieved when Karai shakes her head no — bankrolling the turtles is one thing, bankrolling their kind-of-sister-former-enemy on a shopping trip is kind of another.

"Five finger discount," she says, wiggling her fingers, and then laughs at the expression Casey _knows_ is on his face. "I have money." She looks away. "A lot of money." Then she looks back, a sly look on her face. "You want anything? Foot Clan credit card."

"No. I'm good."

There's a drugstore two doors down from where she wants to go, so when Karai jaywalks over to buy her clothes, Casey follows and ducks through the sliding doors, hooking a basket and heading to the first aid section. He wants to be serious — this _is_ serious — he wants to get as much as he can for as cheap as he can and get out of here and back to the lair, but that doesn't mean that he can't force away a smile when he remembers the time he bought Raph a tube of Bengay and laughed when he told him, in all innocence, that the best thing to do with it was to put it on your balls.

The lady at the registers recognises him from the eighty times he's rolled in here after hockey, so she doesn't ask questions when Casey tips a basket full of off-brand tape and Neosporin out in front of her, and slides him a stack of coupons for next time when she's done. Karai's still not done when he gets back, so he leans up against the wall to wait, digging his phone out of his back pocket.

And winces with guilt at the message from home asking where he is.

His dad doesn't ask for much. Just for Casey to check in, and for Casey to babysit his sister the one night a week his dad goes for a beer with his buddies. Casey can't begrudge him that. His dad works hard, and he does it all on his own. He thumbs out a message — _sorry wont be home for dinner crashing at rafs!_ — and shoves his phone back into his pocket before he can get a reply back.

(It's easier to let his dad think that Casey's hanging around with Raf, the Puerto Rican kid, rather than Raph, the Asian-American mutant turtle.)

When he looks up, Karai is back, watching him with a bag in each hand. "Okay you need to wear, like, a cowbell or something," he snaps.

"Or you need to be a better ninja," she replies smoothly, and smiles. The new clothes she's wearing aren't anything special — a pair of black ripped jeans and a hoodie with mesh sleeves. They look comfortable, and they look easy to fight in.

"April's the one getting the training, not me." He jerks a thumb towards himself. "Casey Jones is a hardcore vigilante of the _night_ , he doesn't _need_ ninja training."

Karai raises a sharp, thin eyebrow, her mouth curving into a sly smile. "Is that so?"

"Yeah." He matches her smile with his cockiest. "It is."

Karai keeps smiling, her lips parting to reveal a slash of white teeth, and her eyes creasing in a way that means _danger_. "I guess we'll find out," she says. "I hope you're right."

* * *

The pet store O'Neil had told them about is small, and stinks of hay and bedding for small animals. Karai had to clear her throat twice before the guy in charge pays them any attention, and then she had to drag Casey away from the small tank full of waddling terrapins.

They lied, of course. Casey made up a story about how he's snake-sitting for two weeks while his neighbour's in the Cayman Islands, and Karai smiled, playing the cute Asian girl who's really interested in the soft, well-fed rabbits they have for sale. Seventy Foot Clan dollars later, here they are, on their way back to the lair.

Casey frowns, hefting the pet carrier. "This is messed up."

"Deal with it." Karai watches the street. No cops, no Foot. As she crosses the street she can hear Casey complaining about jaywalking, and why he has to carry the stupid carrier. "It's those or rats." Either way it's disgusting, and either way it's just another thing she can never, ever tell Leo.

 _Leo_.

He'd recognised her. He'd known who she was. And he probably would have tried to kill her, given the chance. And here she is, buying soft gentle bunnies for him to tear apart instead of his own father.

As soon as she reaches the sidewalk she stops, leaning up against a trashed phone booth until the clench in her throat dies away and her anger comes back, reinforced with the memory of Leo's foaming mouth and snarling hands.

If she can't fix him, she realises, then she'll end him. Either way, she's pretty sure the Leo she knew would thank her for it.

"Uh, Karai? Are you okay?" Casey asks, his brows coming together in concern. He sounds like he _means_ it. Like he _cares,_ his voice soft and cautious.

"I'm fine. Why wouldn't I be?" Karai folds her arms, lifting her chin in challenge. Of course she's okay. She doesn't have any choice not to be okay. But what she does have is her pride, and she doesn't want Casey's clumsy charity. "Look, let's just get this straight — you don't have to pretend to like me just because we're working together on this."

Casey stares, incredulous and offended all at the same time. "I'm not _pretending_!"

"So why are you being nice to me?" Karai asks. "Your little friend down there can't stand me."

"April's got her reasons," Casey replies, in what Karai thinks is his attempt at being diplomatic. "But you wanna help my friends, and that's good enough for me."

"That's it? No other reason, no ulterior motive?"

"Not unless you _want_ one," he shoots back, waggling his eyebrows.

He looks ridiculous, and he looks _normal_ , and it's been a long time since someone looked at Karai as something other than something to own, or to _fix_.

But Casey isn't Leo, or Shredder, and this isn't a game anymore, so the soft twist in her chest needs to be ignored. Right now, Casey is _useful_ , and Karai has a plan to put into action. "Maybe some other time. We've got places to go."

She stalks past the alley without even looking Casey's way. "Uh." He gestures towards the alley as best as he can without looking suspicious, and without jostling the pet carrier. "I thought we were going _back_."

"We're taking a detour," Karai says, and keeps walking.

* * *

 **tbc.**


	6. Part 6

tmnt is property of viacom.

thank you, thank you, a million times thank you - the comments and love this story gets means so much to me - you are all SO GREAT. thank you for reading! we're sort-of at the half-way point!

 _in this chapter_ : plans are put into action. kinda. ish.

* * *

 **Birth of Serpents  
part 6**

* * *

"No," Casey says, folding his arms. Across the street, the church looms, a half-burned shell, and the street still stinks of acrid old smoke and burned wood. "Hell no. I'm not goin' in there."

Karai shrugs. "I know. You're waiting outside." She hands off her bags and leans up, pressing her cool, sly mouth against the corner of his — too close to be a kiss on the cheek, too far to be a _real_ kiss.

She lets it linger just a second too long before tilting her mouth towards his ear.

"You're my _decoy_ , Jones," she says, then skips off across the street, towards the bright nail salon three doors away from the hulking ruin. Casey stares dumbly after her for a long minute, watching as Karai blends into the evening crowd until he loses sight of her.

And then, he gets it.

He's _impressed_ \- he just got _played._

Karai's in a brand-new outfit, no make-up on, her hair soft and ungelled, hanging around with a guy the Foot don't know by face. Kissing him goodbye while she heads in the direction of getting a manicure, and leaving him behind, holding a pet carrier, and a girl's bags, waiting in the street —

He looks like her boyfriend. Standing on the street, waiting for his girl to finish getting her nails done, and keeping watch as she sneaks into the ninja stronghold in case something goes wrong.

Nobody will recognise her. Nobody will recognise him.

* * *

Shredder isn't home. Karai can tell this much as soon as she slips into the ruins, with all of its unfamiliar shadows and acrid puddles, leftover gifts from the fire department the night before. Some FDNY tape flutters in the draughts, and in the new echoes Karai can hear the static-y _yip-yip_ of Footbots, commandeered into making urgent repairs. Somewhere, Bradford snarls, and Xever clanks along, but Karai knows how to stay out of their way. She knows the Shredder's men, and she knows every part of this hideout as much as she knows the back of her hand.

Once, this had been home to Karai. Maybe her room survived the fire, with the little trinkets she'd brought with her from Japan, and the new things she'd bought in America.

She forces the thought away. She doesn't have time for sentiment.

It's easy to slip through the cracks in the security, too. Nobody is expecting her to come home on her own, not when _Hamato Yoshi_ has gotten his claws into her. Nobody's waiting for her, or looking out for her, and so nobody notices when she sneaks her way down into the crypt, down where the cages and the cells are. If they're expecting her at all, they're expecting her to come with friends.

And they don't notice as she creeps into Stockman's newest lab — makeshift though it is, with fire-scorched beakers and twisted pieces of metal.

Even with six hundred pairs of eyes, he's still no match for her.

Karai presses a knife between his wings.

"Hello, Stockman," she says, her voice pitched low. "I have a proposition for you."

* * *

The cushion April steals from the couch is lumpy, the cheap stuffing slowly being chopped up by years under turtle shell, but it's enough to keep the cold away as April sits outside the lab, her legs crossed and her eyes closed. When she had been tracking the turtles through the tunnels, there had been something to latch onto — a thin, vicious thread that they all shared, a twisted sort of hungry madness, but there was still something that made them _them_ , but now they're together, all April can feel is their hunger, and the itching, needling madness.

Once, Splinter had told her to _listen to the silence_ , but there is no silence, just a loud static blur of white noise. Sometimes there'll be something — a bright, tight little glimmer of sound; Donnie's warmth, or a smooth calmness that could only be Leo — but it's like scanning through radio channels on her dad's van's crappy old radio; faint voices, but not enough to really mean anything.

"April?"

She jolts, her senses scattering, then gradually zeroing in on Splinter, crossing the room towards her. In his thin hands he's holding a small cup of tea, and as he gets closer, there are small scabs on the ends of his fingers, where he's picked — or bitten? — his claws down. April locks herself back down before she reads too much. In the back of her throat, she can taste Splinter's fresh grief, and his longing for his sons. He smells of incense and tea and soap, and his robe smells of detergent and the beaten old tumble-dryer that eats quarters like they're going out of style. He's done everything, she realises, to make himself smell like anything _but_ rat. Splinter nods towards the lab doors. "How are they?"

April shrugs one shoulder. "Still in there," she says. "Hungry, I guess."

"Mm." Splinter sips his tea.

She reaches up, scratching at her head. "I keep trying," she says, "but when they're all together it's— itchy. I can't get a lock on them."

"Nor I."

She watches Splinter's fingers tighten around the teacup and chews on the inside of her cheek. Now is not the best time, but it's also the _only_ time she's got. "Karai said she's got a plan," she says, watching Splinter's face and gently opening her mind again, but Splinter has schooled himself carefully; all April gets is a mild curiosity, which is all that Splinter is letting her feel. "I guess she talked to you about it."

"Miwa is a tactician."

"So it's a good plan?"

"All plans are only _good_ until the moment they are put into action." He lets out a slow, deep breath, and rests his hand on April's wrist. "Trust your instincts," Splinter says, diplomatically. "You must not let your anger blind you."

April curls her hands up. It's not like she was expecting Splinter to suddenly turn and tell her how much he agreed with April's assessment of his daughter, but she can't help the nagging feeling in her gut — Karai doesn't _deserve_ Splinter's loyalty. The turtles have fought and bled for him, it's the turtles who brought Karai home. Now Karai's here trying to take charge, and Splinter's okay with that, and April wants to rebel against literally every word she says.

Some other time, April would laugh — once, Leo came to her fire escape to whine about Raph: _it's like everything I say he wants to do the opposite_ , he'd said, flinging a hand up in despair. _Raph, go left. No, Leo, I'm gonna go right, because I always am._

 _Red hair, red mask_ , she thinks wryly.

But Karai isn't Leo. Karai is not April's leader.

She forces herself not to sigh, and turns back to the door.

There's been a shift in the room, like wind on sand, and very gently, something presses against the heavy metal doors.

"April?" Leo asks from behind the door. "April, are you out there?"

He sounds so _normal_.

April glances at Splinter, waiting for advice, or an order: he nods once.

"Yeah," she says, the word tripping in her throat and coming out in a stammer. "Yeah, I'm here, Leo."

The door rattles once. "We're locked in." Rattles again. "The keys aren't here." Rattle rattle rattle. "Donnie can't remember where he put the spares." Leo's voice is achingly familiar, and warm with exasperation; Donnie always misplaces things when he's zoned in on a project. April's found wrenches in the bathroom, a blow-torch under the sink and, one time, a physics textbook being used as Ice Cream Kitty's new scratch-pad. "Can you let us out?"

April glances to Splinter, who returns the look gravely. "I can take a look in his room," she offers, forcing herself to sound light. "How are you guys doing?"

"Okay," Leo says. "Getting a little cabin-fever in here, you know how it goes." He laughs a little. "Not like _you're_ a stranger to being rescued from lock-up. Think you can return the favour?"

Whatever April was expecting Leo to say, it wasn't that. Her heart wrenches, sharp and dull at the same time, and the next few beats _ache_ with hurt and betrayal. Yes, the turtles have rescued her, more times than she cares to count, and more times than she wants to remember. They've dragged her out of the back of a van, and they've dragged her away from a needle about to tear into her brain while the Kraang stood around, watching and laughing at how afraid she was, but the turtles have never, ever mocked her about it, and they've never tried to _blackmail_ her with it.

She had never thought that they would. She had never thought that _Leo_ would.

"Yeah," she chokes out, her throat dry with hurt. "I can take a look for the keys. Where would Donnie keep them?"

Leo hums thoughtfully. "I guess the kitchen?" He taps gently on the door, a soft four-time beat. "We're hungry."

Her gut sinks. "Oh?"

"Yeah."

"Casey went to get you guys something."

"That's nice of him. He doesn't need to go far though." The tapping gets a little louder, a little more erratic: _tap-ta-tap-tap, ta-tap-ta-ta-tap._ "We can eat what's in the lair. All you need to do is let us out."

"I can't, Leo. You know I can't do that."

"Donnie's hurt, April." _Ta-tap tap, tap-tap_.

"I know."

"Open the door."

"I can't."

"Donnie would help _you_." Leo spits the word out, like every time they did help her, it was a chore. "We always help you, April. Why can't you help _us_?"

April swallows, and before she realises it, her vision is glassy and her eyes are full.

It's Leo, but it's not Leo, and it's Mikey, but it's not Mikey, and somewhere in there too is Raph and Donnie. "We're trying," she says, her voice coming out on a breath that bottoms out on her, sucking all of the air out of her chest. "We've got a plan."

Something slams into the door — a fist. Leo hits the door again, and again. "Open the _door_!"

" _Leonardo_."

Splinter rises to his feet, crossing to the lab door as Leo's voice trails off into angry, hungry hissing. " _Rat_ ," Leo says, the tapping on the door warping into slow slides of snake coils.

Splinter sighs. "Leonardo," he says, his voice steady even as his sons hiss as one behind the door; twelve furious, angry, _hungry_ mouths.

* * *

"You bought bunnies?" April asks when Casey shows her the carrier. She's been off since they got back, tension in her neck and her shoulders, but when Casey cheerfully held up the pet carrier, she just looked grossed out, her mouth pulling down and her face crinkling up.

Casey shrugs, vaguely itching at the side of his mouth. "Bunnies or a bag of rats," he says, handing her a hockey stick. "Guess which one I'm not taking on the subway."

"I guess, but…"

"This is all we could get," Karai interrupts. "Take it or leave it."

" _I'm_ not the one who has to eat them," April snits back, and Casey clears his throat before the bitching starts. He picks up the carrier and heads over to the door, tugging loose the heavy lock and chain.

Karai steps up, thin fingers pulling at the chain until it slides free, and Casey eases through the door, bat in one hand, carrier in the other.

The lab is eerily still, all four brothers with a corner each, so with Karai and April watching his back, Casey carefully sets the carrier down, opening it and grabbing a few pieces of straw. He waggles it into the rabbits' faces and _tut-tut-tut_ s to try and coax them out. As Duracell and Lunchmeat hop into the lab, little bunny noses whiffling gently at the air, Casey feels the hair on the back of his neck start to prickle.

Mikey still hasn't moved, still a turtle, still staring coldly ahead, and Leo is awake now, too, watching them from his corner. Donnie raises his head, watching with interest as—

"RAPH NO—"

— as Raph lovingly bodyslams Casey to the ground, and rests his jaws on Casey's hair. "Raph," Casey grouches, worming his way towards the lab door with his toes when shoving Raph's face doesn't work. "when this is fixed _we are gonna have a serious talk_."

Raph doesn't give a sweet shit, apparently, because when Casey gets to the door, Raph doesn't let go, winding himself even tighter around Casey's legs. "Raph, _c'mon_ ," he complains, hauling himself up by clinging onto the door. "you're not allowed outta the lab." He gestures to Karai and April — _a little help here?_ — but even though April looks ready to swing, they don't move, watching to see what Raph does next.

Casey is so, _so_ glad that they manage to work shit out between them at a time when it really matters.

And then Raph does it.

 _Again_.

He does the _eyes_. Big, sad green eyes and his tongue peeks out the tiniest bit and he huffs through his nose and squeezes Casey's thighs just that little bit tighter: _c'mon, Case_ , he doesn't say, _don't be a dick_.

"Fine," he mutters, penguin-waddling out into the lair with Raph still wound around him. "But if you start trying to eat me, I _will_ shoot you in the ass."

* * *

Raph, it turns out, is totally fine to eat pizza instead, and the bonus of him being a snake means he can't bitch about the fact that the pizza is frozen. Casey just pulls it out of the oven, rolls it up, and Raph, his big dumb turtle-snake-dog, snatches it out of his fingers before Casey even gets a chance to put it on a plate.

They keep Raph away from the dojo. Casey puts a trashy movie on TV and aside from when Karai comes back from taking Splinter his dinner, Raph barely seems to care. Even then, all he does is gently sniff at Karai, his tongue flickering out once as though the hint of rat on the air is enough for him, and then flops back down.

Half-way through the movie, April's dad calls. She heads out to take it, and as she disappears down the tracks, Casey takes his chance. "So, are we gonna talk about what happened earlier?"

"What's to talk about?" Karai asks. "We had an opportunity and I took it."

"You _ditched_ me!"

"No, I put you on look-out while I infiltrated."

"Yeah, that wasn't in the plan, sweetheart," he snaps back. "The plan was-"

"I _know_ what the plan was," Karai interrupts. "But plans _change_. Are you seriously saying that we should have come all the way back here just so that O'Neil can come _back out_ and join us?"

"Red's a part of this too," he says, sullen and stubborn. At his feet, Raph lifts his head and hisses once. Whether Raph can understand them or not, Casey's pretty pleased by the back-up: _argue with me and you argue with my giant snake here_. "You can't just bench her."

"I know she's in this. I also know that both the Shredder and the Kraang are after her. So if we want to take her anywhere near either of them, we're going to have to be ready for a fight. Which we're not."

Casey doesn't answer. She's right, though he doesn't like it, and doesn't want to admit it. April's a liability, and the turtles aren't here to have her back.

"Besides," she adds. "I got what we wanted."

Casey looks up at that. So does Raph. "Yeah? What'd it take you?"

"A little persuasion."

Somehow, Karai manages to make _persuasion_ sound like _I cut out an eye and threatened the other one_ , and it's Karai, so that's totally possible, and Casey tries to not be impressed, but it doesn't work - he _is_ impressed. Karai is _dangerous_ , and Casey _lives_ for this stuff. It's not hard to imagine what it would be like to take her on, or, even better, to team up.

Guilt rises up again. They're supposed to be a _team_. "So what do we tell Red?" he asks.

A flicker of… something runs through Karai as Casey watches her. It's not quite uncertainty, but it's not nothing, either, when she flicks her eyes over to the turnstiles, like she's expecting April to just come home like she was summoned. "We tell her there was a change in the plan. Tomorrow," she clarifies. "It's late."

Raph huffs - it's a cop-out, and the three of them know it.

Karai gets up, all of her stretching. Her new shirt rides up, showing off a strip of pale, taut belly, and Casey forces his eyes north, the corner of his mouth tingling. Karai smirks. "Don't stay up too late," she says, before slinking off towards Leo's room.

Casey waves her off, turning back to the TV. It's a _really_ crappy movie, with more crying than explosions, but for the most part it's keeping Raph quiet, and while the final fight scene plays out, April heads back into the lair. She's dressed in her pastel pyjamas, and her hair's still damp from the shower. When she sits next to him, she smells like shower gel and cold wind, and Casey's heart jumps a little, and it's not just from guilt.

"All good?" he asks.

April shrugs. "I guess. Did you call home?" she asks instead.

Casey nods — call's a nice way of saying _I texted my dad and then ignored any replies_. "Tonight's okay, tomorrow I've gotta go to practise for an hour."

April pulls her mouth into a frown. "Casey…" she says, and he shakes his head before she can start.

"I can't lose my place on the team, Red."

"And the _turtles_?"

Casey can't help himself. He loves April in so many ways, but she doesn't _get it_. The only people she needs to hide her weird life from are people in school like her creepy friend Irma. The rest of her life is one big long alien parade. Casey doesn't get that kind of luxury.

"Okay, here's the thing," he says, turning towards her. "You and your dad are like, smack in the middle of all this. You guys know _everything_. But my dad would move us out to Jersey if he figured out I was hangin' out with mutants after school. And like, not _good_ Jersey. Bad Jersey. _Jersey Shore_ Jersey. You think he wants my little sister involved in _alien invasions_? He would _literally_ be happier if she turned into Snooki."

"You think my dad hasn't talked about moving upstate?" April counters, her cheeks heating. "My aunt got a permit and goes on conspiracy sites trying to find out if real guns work on _real aliens_. And she _doesn't_ know."

"That's _different_ ," Casey cuts a hand across the air. " _He_ knows."

"Yeah, but Casey—"

"All _you_ have to do is say _hey dad! I got a turtle thing!_ And he'll be like, _sure thing, pumpkin, don't let Donnie do your homework!_ "

"You know _how_ he knows?" April snaps, her face red but her lips white, and Casey's stomach bottoms out the way it always does when he knows he's fucked up. "He _knows_ because the Kraang held him prisoner for nine months. And you know what happened after?"

Casey knows.

And what he doesn't know, he can guess: the days that April comes into school with circles around her eyes and he sits in front of her in first period so she can sleep, and the days that she detours on the way home to pick up her dad's meds, and the time Mr. O'Neil took them out somewhere fancy on April's birthday and wore a quiet, hunted look when three Wall Street goons in crisp pinstripe suits took the table behind them.

Casey knows, but that doesn't stop him feeling like shit when April tells him: "He got turned into a _giant bat_ who ate trash and attacked people and _there are videos of him on YouTube_ _doing it_. So _yeah_ , my dad knows, and do you even _get_ how much I _wish he didn't_?"

"Red—" Casey clenches his fists. "I'm sorry."

She doesn't look at him, sniffs once. "It's fine."

It's not, and he says as much, reaching over to run the backs of his fingers against her arm. "Red," he says again, and then, "It's gonna be okay. We're gonna fix this."

This time, April shoves his hand away. "We _have_ to," she says, and draws herself up. "I'm going to bed."

Casey watches her go, slipping quietly into the dark and into Donnie's room. The door barely clicks, and when she's gone, Casey snarls deep in his throat, slamming his heels into Raph's beloved beanbag. It doesn't help, and all it gets Casey is an affronted look from Raph, all like, _what the hell, Jones, don't trash my stuff_.

"Whatever," he mutters, turning towards the bedrooms himself and patting his thigh until Raph obediently slithers down the hall after him.

* * *

The door closes behind April with a soft _click_ , and she takes a deep breath, waiting for and letting the wrench roll over her as she catches the scent: sleep, sweat, Donnie.

Donnie's room is the smallest out of his brothers, a trade-off for being allowed the whole lab. His bed is shoved against the wall, and instead of a bedside table there's a stack of old college textbooks that he'd finished with and couldn't find any other use for.

Back when Karai was hunting her down, Donnie had set up a camp-bed in the lab for himself, letting April have this room. She'd always associated Donnie with being _safe_ ; Donnie had been the one to catch her, the one to guard her, but that one gesture, of Donnie giving her _his space_ , had meant more back then than she could have said. He hadn't complained, not even when she'd started burning scented candles in there that made him sneeze, the scent of lavender clinging to his skin weeks after she'd moved back home.

One of his shelves still has them, the wicks curled and burned. The sight of them makes her stomach hurt.

She shuffles over to Donnie's worn old bed, stepping past the bits of mess on the floor, all of the little pieces that he hadn't tidied up— and why would he? He'd thought he would come home; the empty milk carton could have been trashed tomorrow, the shelf of keepsakes could be dusted another time.

April almost wants to clean things up for him. Donnie's walls are full of photographs, and the shot of him and his brothers is slightly askew, the one of just him and Master Splinter is a little dusty. But cleaning things up means that Donnie won't — can't — do it himself, and April's been through this twice already, leaving her dad's coffee untouched on the kitchen table until the milk in it rotted, and wearing his beaten old jackets to school until her aunt pointedly took her to Macy's.

She curls around one of Donnie's pillows (Donnie falls asleep on his back, rolls to his side, wakes up on his front; April knows this the way she knows the ghost-like imprints of him left around the lair, the way Donnie's love carpets his home and keeps his brothers warm, and the fierce, dogged loyalty that keeps them defended, and the way Donnie has to stop himself, every time, from brushing her hair out of her eyes; it's all there, in the things that Donnie won't — can't — say), and now that she's alone, and the day is over, she can cry for real, grief seeping out of her like a slow-deflating balloon.

They have to fix this.

She scrunches her eyes shut, biting hard onto her knuckles to muffle the sound.

They have to _fix this_.

* * *

It's maybe an hour later when April wakes up again.

Her eyes sting, and her cheeks burn from the salt, but they're not what wakes her. It's an ugly, cold slither in her gut — a premonition.

Sure enough, five seconds later, a jolt of terror cuts through her head, and even before April has recognised it for what it is, urgency throws her out of Donnie's bed and towards the door. As she slams into the hallway, she almost crashes into Casey as he yanks open Raph's door; inside, Raph rears up and hisses, scared and angry in equal measure. "What—?" Casey asks, in an awkward mix of sleep and urgency, and April doesn't even get time to tell him to put his pants back on before a snake starts to howl.

Donnie howls, in his normal, turtle voice, while his brothers hiss and spit and tear into him.

* * *

 **tbc.**


	7. Part 7

tmnt is property of viacom.

we're just about the half-way point of this story now! thank you everybody, again - I try to reply to reviews via PM and if I missed you I'm very sorry. feel free to hit me up with talk or just general turt-babbling!

 _in this chapter_ : things go slightly wrong and April does a thing.

* * *

 **Birth of Serpents  
part 7**

* * *

Karai doesn't have time to be impressed.

By the time she's out of Leo's bed, armed, and into the main room, Casey is loading tranqs, O'Neil is pulling at the heavy chains to the lab, and her father lingers at the ledge over the tire-pool. Everybody's in place, knowing what to do without her having to say a thing.

Casey straightens, the tranq gun held in his left hand, and steps aside as she lands neatly next to him. The hissing is now guttural snarling, and Donnie's howls are now bitten off sounds that don't count as sobs, but aren't horrified enough to be screams; instead, they're just sad and resigned — Donnie is making all of this noise because that's the only thing he can do.

O'Neil gets the last loop of chain off of the door, and Karai holds up her hand. O'Neil starts to look mutinous, but Karai knows that she knows what she's going to say: "This could be—"

"A trap," Casey finishes for her. He preens, twirling the tranq gun around his fingers. "Yeah. We know."

When Donnie howls again, Karai gives the signal. O'Neil pulls the door open and Karai catches a glimpse of Leo and Mikey standing over Donnie's shell, their hands bloody, before she throws flash-grenades through the gap.

While the turtles hiss and snarl in pain, Karai throws down a smoke-grenade too, and she and Casey slip through the door.

In the smoke, it's difficult to see much of anything, but Karai can hear the _thunk-thunk_ of two tranq-darts finding their mark. When the air clears, her brief relief at this fight _maybe_ being an easy one sinks down to her gut - Leo and Mikey have turned their backs on their brother, their shoulders are taut, and their bodies are tense.

Leo reaches up, plucking the dart from his bicep, and throws it down. The metal _clink_ echoes in the lab. Karai ignores it, the same way all four of them are ignoring Donnie's shaking gasps in the corner, even as the sound curls around them.

Leo takes a step forward, his eyes narrowing as Mikey watches, and Casey laughs, a low, short _he-eh_ before he beckons with his left hand. Lunging, Leo takes the bait, his hands reaching for Casey and snarling when Casey ducks out of reach and across the lab.

Karai turns to Mikey.

Karai knows Leo - knows how predictable he can be. She doesn't know Mikey, but she doesn't want to take chances, not while Leo is throwing himself at Casey. She kicks off from the ground, already reaching for her sword, and the white membrane slides over Mikey's eyes.

Mikey is faster than Leo, and the fact that one bite could end this means that Karai has to change her default strategy of beating the turtles and beating them as quickly and as humiliatingly as possible. Instead, now it's a matter of making Mikey move long enough that the toxins in his bloodstream take action, and he goes down that way instead. So the sword in her hand isn't her trusted blade anymore, and the lessons she's learned are the wrong ones.

Mikey, too, is _wrong_ \- she's never fought him, but she's watched him. Mikey is loud and brash and erratic. He wastes time and energy, focusing more on flair and fun than finesse - he kicks twice when one would be enough, and backflips when he should throw, and laughs when he needs to be _quiet_. But this Mikey is silent. His eyes are white as he comes at her, his mouth drawn into a tight line, and her heart freezes in the second that she blinks and Mikey is already throwing a punch at her throat.

She blocks his arm with the back of her blade and pushes him off, flinching despite herself when the sharp edge of her sword grazes his bare wrist before he springs back.

She doesn't want to kill him, after all.

Mikey says nothing. But he looks at his new wound, and then back at her. His eyes narrow.

Across the lab, Leo staggers as the dart finally kicks in, his knees buckling underneath him and sending him crashing heavily into one of the tall stools. "Casey!" O'Neil yelps, and Casey vaults the desk to where she's holding up Donnie's body, her hands under his arms and locked over his plastron.

Mikey doesn't pay them any attention, but Karai can tell in a twist of his muscles that he thought that _she_ would; he arches slightly, as though to head in the direction of the lab door. So Karai feints that way, and then twists to the other side.

Mikey sways a little as he turns — the tranquiliser is starting to work; slower than with Leo, she notes — and she takes advantage of his momentary weakness to curl her fingers and slam the heel of her palm up into his face.

"Ow!"

Mikey claps both hands to his face, staggering, and Karai stops, her hands raised in front of her in defence, waiting to see what Mikey does.

What Mikey does is _whine_.

He sits crosslegged on the floor and gently dabs the base of his palm against his face, checking for bleeding, and Karai can almost hear his stuffy-nosed complaining — _you hid mai dose!_ — and smirks despite herself.

She doesn't get cocky. She keeps her distance, and waits. There's no way that she just smacked the sense back into Mikey, no matter how much she might like the idea.

She's right.

An arm blurs out to the side, longer than it has any right to be and still stretching, and when Mikey hooks his elbow back, it slams into the backs of Karai's knees. As she goes down, she throws her hands out behind her and backflips out of it. She's backflipped thousands of times before; she is elegant, she is precise, but when her feet hit the floor again, Mikey swarms her, his whole body melting together with his legs and shell blurring into one long serpentine body. His jaw, still part of a turtle's face, unhinges.

Mikey's coils squeeze and the air wheezes out of her lungs in a rush, and then he squeezes tighter: she can't breathe, and she can't make a noise. She can't reach the small blade in her sleeve or the one at her thigh. Mikey's face presses closer to her, his mouth widening, his tongue flickering, his teeth sharp and glinting with spit and dim light.

 _He's going to eat me whole_ , Karai realises, and she still can't scream.

She has never imagined her death to be so _quiet_. She's been raised by fire and steel and blood, and dying in silence seems so _cheap_ —

The weighty _thunk_ of a second dart hits Mikey's neck, and his teeth clack together as his mouth slams shut. The tight, cruel twist to his face slips, his body uncoiling and flopping ungracefully to the floor around Karai's feet.

"Karai," Casey says at the door, his voice blown-out. Through the gap, Karai can see Splinter on the ledge, his hands twisting. Donnie and O'Neil are gone. She turns back to Leo and Mikey, both out cold, and can't shake the feeling between her shoulders that there's something missing here, that _she's_ missing something. "Karai, c'mon. Get out."

* * *

All of the turtles have scars. Every time Casey's next to Raph he can pick up on new ones; a set of tarmac scrapes along his plastron, or rug-burn on his forearms, or a twist on the way Raph walks that indicates he pulled his knee again. Mikey has scrapes in his shell too, though less than the others. From the few times Casey's been close enough to Donnie to see, his scars are mostly along his forearms — a couple of slashes from fights that got past his bo, and spattered burn marks that probably come from whatever weird stuff he does in the lab. One really cold night, back when Casey first got to know the turtles, Donnie favoured his left shoulder; other than that, Casey's pretty sure that most of Donnie's injuries have just been bruises, mainly on his pride.

Now, though, Donnie's legs are covered in deep gouges, and his blood is congealing, black and thick, between his toes.

Donnie doesn't move as April stitches up the final tear in his arm. He watches, and shifts obediently as she tells him to hold still, or to lift his arm up, but it's like he's so far gone he doesn't even feel anything; he doesn't flinch, or wince, or even hiss even when she pours antiseptic onto the thick tears down his arms and legs.

"Okay," April says, cupping her hands around the bloody tissues and cotton balls. "That's about as good as I can do." She casts an eye at Donnie's feet, then back to Casey. "He should probably shower."

Casey fidgets. "Yeah, I can do it," he says, because he knows that's what April wants to hear, even though lovingly giving Donnie a sponge bath is just one of the few things Casey never wanted to have on his bucket list. But Splinter can't do it, and something slithers, hot and jealous in his chest, at the idea of April doing it.

The smile he gets from her, though — tired though it is — is worth it. "Maybe give him a minute for the stitches to settle?" she offers, dumping the used-up supplies in the trash and scrubbing her hands.

Casey shrugs — Donnie's not going anywhere — and crosses the kitchen to the freezer, yanking the door open. Ice Cream Kitty yowls miserably until Casey chucks her gently under the chin, and she purrs while he reaches for the box of frozen pizza that Mikey once stressed was _only for emergencies, bro, like Godzilla, and nukes, and Fleet Week_ , when the turtles couldn't go topside because all of Manhattan was drunk and awake until 3am. When he closes the freezer door again, Donnie is watching him, his mouth open slightly like he's about to say something, but the words don't come, and Casey turns towards the oven. "You doin' okay?" he asks quietly, shoving the pizza onto a dented baking tray and lighting the gas. April sucks in a deep breath, her shoulders straightening before she nods sharply. He takes it for what it is. It's better than she was before they went to bed, at least. "You get any sleep?" he asks, and April doesn't answer.

He looks at the clock on the microwave. It's barely 3 in the morning, so no wonder April looks like hell. Her eyes are baggy and bruised, and there's a smudge of blood down her left pyjama sleeve that Casey isn't going to tell her about. Instead, he stretches up and pulls open the cupboard above her head, revealing the catering-size tub of instant coffee and sets the kettle boiling.

Casey's been meaning to make coffee for the past half hour, ever since Karai knocked down April's slow spiral into _we should have put Donnie somewhere else, this is my fault_ by shoving the medbox at her and swanning out of the kitchen to talk to Splinter. But then April needed his help, and the coffee got abandoned while they patched Donnie up.

He shoves a tablespoon of coffee into three chipped, scraped mugs, one each for him, April and Karai, then sloshes milk into two. Then he glances at Donnie — Donnie who eats this stuff when he thinks nobody's looking. April subtly shakes her head, and Casey nods. No caffeine for the crazy snake boy.

Donnie doesn't even look like he _cares_. Just keeps staring ahead, even when Casey pulls down the bag of brown sugar and tries to hack off a piece with his spoon.

April slides her own mug (Donnie's mug, Casey realises, black coffee and all) away and sips it carefully. "Maybe if we put them both in the lab," she suggests slowly. "I mean, Raph was _protecting_ Donnie in there. Right?"

Casey shoves the sugar back in the cupboard louder than he intended.

It doesn't sit well at all with Casey — if Raph was _Raph_ , there's no way he'd have left Donnie, not knowing that Leo and Mikey were getting ready to go full Hannibal on him.

But Raph's _not_ Raph.

Raph's never been scared of his brothers a day in his life, Casey doesn't think. Raph is loud and noisy and he's got arms so thick he could crack a walnut by flexing. This Raph, the Raph who clings to Casey like a beloved plushtoy, and who right up until things went down with Donnie was trying to snuggle up to Casey in his sleep — this _isn't_ the Raph that Casey knows.

"Yeah," Casey says, dragging the word out and setting the kettle down before he's even poured it. "I'm not sure he was."

"What? _Why_?"

Casey shrugs. "You don't think _Raph_ would have stayed?" he asks. He doesn't need to, but he waves at the older tears on Donnie regardless, the ones that they cleaned up the first time and that have half-healed already, leaving shiny pink-green scars along his shoulders and thighs that glimmer in the kitchen light. "First chance he got, he booked it outta there. And it's not like he's breaking the doors down right now to get here and kiss it all better."

"But he—"

"Snakes nest," Casey interrupts. "Saw it on one of Mikey's nature shows. They do it to stay warm."

Mikey's nature shows are the one show that _all_ the turtles agree on watching — Donnie downloads them in big torrents and they sit around and listen to some old English dude talk about the majestic African plains while watching lions tear pieces out of zebra.

"Then where do we put him?" April asks.

His shoulders hunch. Sure, they could put Raph and Donnie together, but who's to say that next time Raph won't take a turn trying to get a chunk of Donnie for dinner? The dojo is a no-go, and it's not like April and Donnie can bunk together, either.

"Donnie's _smart_ , and—"

Donnie can get himself free if he has to. There's no lock Donnie can't pick, and if Donnie's still in there, that means that Donnie can still get out.

April doesn't say anything after that, trailing off and her eyes unfocusing — it looks, Casey thinks, like she's thinking the same thing he is, and how do they even check something like that? How much of Donnie is still _in_ Donnie if all of Raph is gone?

Casey breathes in again; the kitchen smells of dusty concrete and industrial floor-cleaner, and the salty smell of pepperoni in the oven is undercut by the sweet stink of the compost bin in the far corner.

And the smell of coffee, and blood.

One of these things is not like the others.

Casey sighs. "C'mon, nerdzilla," he says, brushing himself off before reaching and gently, firmly, taking Donnie by the wrist. "Let's go clean you up."

Donnie plods slowly, a step or two behind Casey. If he's pissed about Casey being the one to clean him off, he doesn't show it, but without the mask, and the kneepads, it's hard to not look at Donnie like the giant walking mutant he is, all scales and green skin and green eyes — there's _nothing_ about him that looks human.

* * *

Later, when Casey has Donnie showered and dried off and the worst of his wounds are bandaged in fresh white gauze, they sit around the kitchen table again and talk.

"I dunno if this is a good idea, Red." Casey chews on the leftover pizza crust, pressing it up against the gum where his front teeth used to be. It helps him think; the bread digs into the soft meat in his mouth and keeps him focused. Across the table, Donnie stares at the piece of oven pizza in front of him, and Casey wonders — is Donnie not hungry because he just got wrecked by his brothers, or is Donnie not hungry because he's the one who ate the rabbits?

April shoots a quick look in Donnie's direction, then turns back to Casey. "It's the only idea I have. And he's right here."

Casey nods. He gets it. But— "But what if Karai's got a plan?"

"Then she should have _told_ us," April snips back smoothly. "I can get in there, Casey. I know I can."

Casey forces the wince down from his face and into his stomach, his gut clenching once. Karai took one look at Donnie when they got him into the kitchen, and then went up to the dojo to talk to Splinter. Things have changed again — first there was Stockman, and now there's Donnie, on his own two feet and barely talking. They need to sit down and regroup, probably, but honestly, Casey's not 100% sure how that will go.

Because April still doesn't know about the detour they made last night — that Karai made last night. She's still working against an old plan.

"Yeah, but," he hedges, then stops. He's not going to sell Karai out, but at the same time…

"This is _mine_ ," April adds, and there's more fight in April's voice than he likes being aimed his way. This isn't her usual _Casey I will end you_ , instead, it's _Casey stay out of my way_ and he doesn't _want_ to be in her way _or_ out of it — they're partners in this, and if she's going to do anything, he's going to be backing her up, or at her side, or both.

April's never been clear on what exactly her brain-powers are. All Casey knows is that sometimes April knows he's had a shitty day even when he's tried his hardest to hide it, and she knows to drag him down a different hallway in school seconds before Nick and the rest of Casey's old group of friends head towards the lockers, and once she blew the Kraang up using only her brain. She spends an hour with Splinter three times a week training alone, no turtles allowed.

(He's not entirely sure what, exactly, turned April from _soulless redhead he never paid attention to in class_ to _Actual Anime Character_ , but he's not exactly complaining, either.)

If there's something April can do that can fix this, or at least get through to Donnie without him ripping their faces off, they may as well try.

"What do you need me to do?" he asks, wiping the pizza grease off his fingers and onto his shirt.

* * *

There's nothing in her father's library of scrolls that talks about fighting off a forced mutation. Karai had watched as her father's ears had flattened as he flattened out the three he could find about demonic possession, but amid the flaking old ink and soft, worn papers, there was nothing there that looked like it could help. They spoke of the afflicted focusing his own ki, rallying his own spirit to fight off the invader. When Splinter had looked at her with tired, sad eyes as he restored the scrolls to their hiding place, Karai had felt the ugly slimy sensation of an impending failure rippling under her skin.

Very carefully, she had laid out her new alterations to her plans, now that Stockman is dealt with and Donatello is back in his own shell, and watched Splinter _hm_ gently under his breath, give some gentle points of advice, and say nothing else.

Now that Splinter has gone back to bed — where he won't sleep, Karai's sure of that; he'll meditate and wait for the next thing to go wrong — Karai's realised that he's left her plans in her hands.

Back with Shredder, he would drill her again and again — what would she do if one aspect failed? How would she accommodate for unreliable intel? How would she punish for it later? And even when she was sure her plans were perfect, she knew that Shredder still was watching her, receiving reports of her successes and failures, making sure that his heir was worthy.

Instead, Splinter _trusts_ her.

She's not altogether sure how to work with that.

The lair is dark and quiet when she slides the shoji closed. O'Neil and Casey are still in the kitchen with Donnie, which means they're occupied, which means that there's a good chance of her not being interrupted for a long while. Karai slips across the main room, her feet silent and sure, and she stops just outside of the lab, listening to the sounds of breathing inside.

"Hello, Leo."

In the lab, she can hear someone stirring, dragging themselves up with the scuff of shell on concrete. Leo's voice comes a moment later, rough and groggy. "Karai."

The tranquiliser wears off quicker and quicker each time as they adapt to it. Soon, it'll be useless. The box next to the door is already starting to empty — Karai's just not sure which will be first: the darts running out, or the darts not working.

"Where are Raphael and Donatello?" Leo asks. Karai doesn't reply — in truth, she doesn't know how to reply to that ( _one of them is bleeding out in the kitchen, and the other is hiding under his bed_ ), but as she chews over a potential reply, Leo says, "Oh, that's where they are," and then scoffs, as though of _course_ that's where they are — they couldn't be anywhere else.

Karai straightens her shoulders against the shiver that chases up her spine — she's been trained to be stronger than this, a better ninja than this, with no time for sentimentalities, but something in Karai needs to see Leo's face, even though she knows she'll see nothing of Leo _in_ that face.

No matter what she's done to him in the past, Leo's always tried to reach her. It was only two nights ago that Leo looked at her through the bars of her own cage — she owes Leo a debt. She owes Leo a _chance_ — one for every chance he gave her. "Can you behave yourself?" she asks, her fingers carefully tracing along the cold metal of the padlock.

"No," Leo replies, short and simple. "Not the way you want."

"Okay," she says, and picks the lock.

She wraps the chain differently this time, so it's loose enough to open the door a little, but not loose enough that any part of Leo could get out. When she eases the door open, and the chain strains, she steps back. Karai is not an idiot; she is not sticking her face up against where her enemy can see her.

And Leo is an enemy. As much as she doesn't want him to be, he is, and he's more dangerous now than he ever was back when he really _was_ her enemy.

Through the gap, Leo — bruised, blank-faced — stares out, maybe a sword's length away from the door. He doesn't move. Behind him, Mikey stares at her, his third eyelids still down, but the way the light hits him makes his green eyes shine through the membrane, giving his face an eerie glow.

"How did you sleep?" she asks, and Leo smiles. "Should I ask about why you attacked your own brother?"

Leo just keeps smiling, his mouth shifting into something thin and _mean_ , the type of smile Karai's used herself, when she wanted someone to just talk themselves into their own grave.

"Man on the outside?"

Still, a smile.

"You know we're going to be watching him. If you're expecting him to get us in our sleep, then that's not going to happen."

"Then bring him back," Leo offers. "We can deal with him instead."

"That's not happening either." It's not exactly subtle what Leo means when he says _deal_. "But if you want to make a deal, I have an idea." Leo's smile fades slightly. He raises one eyebrow, and Karai keeps going: "I want the smart one."

"Donatello," Leo fills in, then frowns. "Why?" He says it like the very concept of needing Donnie for anything is beyond him. "He's _weak_."

"He's smart," Karai replies. "I need to use him."

"And what's in it for us?"

"The rat," Karai says.

Both Leo and Mikey's mouths curl up in the same, vicious smile. It's unnerving in its cruelty — the cat enjoying watching the mouse scream before deciding it's bored of playing, and not entertained enough to strike the killing blow. "We don't need your help getting the rat," Leo says. "Sooner or later, we'll get out of here. And then we'll get him."

"Or, you could do what I want, and then you get him sooner. Besides, the smart one's still got a job to do."

"The retromutagen," Leo agrees. "But we don't really care about that anymore."

"But _I_ do. And _I_ have the keys."

Leo tilts his head back, so that even in the dim light of the lab she can see the small dark flecks and ridges on his snout where his nose is, and he breathes in, long and slow — smelling her. Her stomach rolls, repulsed, but she keeps her feet firmly on their spot. "That's not like you, sis," Leo says. "I thought you were a good girl now."

"Maybe I am," Karai says lightly. "Maybe not. But I think it's a fair deal. You four tore up half of the city. All I want is for you to give me control of him for a week so we can fix everything you broke. Then, you get the rat. Isn't it better to eat healthy prey than something you've let rot for a week first?"

Leo turns to Mikey, and something unspoken runs between them. Mikey's face doesn't shift, still cold and blank, but after a moment, he nods, lifting his chin in agreement.

"We want the rat," Leo says.

"And you'll get him. But not until I get what I want."

Leo goes still, his shoulders pulling back, taut, and the tendons in his neck popping out. His eyes, still wide open, roll back, until there's none of the split pupil, just thick acid green. He's silent, and as Karai looks to Mikey, he's doing the same thing.

They're _communicating_ — Karai realises this a moment before Leo fixes his eyes back on her. "Okay," he says. "Take him. But we're waiting."

* * *

Once Casey has stood in front of the kitchen's main door, the one closest to the dojo, April takes a deep breath through her nose and steps closer to Donnie, all of her senses trained on him. He doesn't move, but there's a thin spike in the air that tells her that he's _noticed_ her.

She raises a hand.

Instead of attacking, Donnie reels back, the stool clattering behind him as his shell clacks against the counter-top. Casey starts, all of him flaring up ready for a fight he really doesn't want, but April shakes her head. "Donnie," she says, as gently as she can, and those green eyes focus on her. "It's okay. C'mon, just—" She reaches out, and Donnie hisses at her. It's a warning, and April heeds it, carefully backing off in small steps until Donnie calms down again.

Behind her, Casey snorts softly. April whips her head around. "Seriously, Jones? You think this is _funny_?"

Casey waves a hand in front of himself, his face twisted up into the _I'm-not-gonna-laugh-but-only-because-I-like-not-being-murdered_ face that he uses half the time in school. "No, no, it's just— you gotta laugh, right? Snake Donnie?"

April raises an eyebrow, and Casey drops into a wheezing cackle before rapping, " _The Donaconda don't want none_ —"

"Oh my _god_ ," April groans, pressing the heel of her hand into her forehead and turning away from him again. "Can we _focus_ here?"

"Okay, okay," Casey shakes himself out behind her. "Focused and ready."

Donnie is still pressed up against the countertop, watching them. His eyes are fixed on her, and his breathing, still a little harsh, hisses through his slightly-open mouth. She can still see his teeth.

But.

This is _Donnie_. "It's okay," she says. She's not sure which hurts more, the idea that Donnie would hurt her, or the idea that Donnie would be _scared_ of her, but she presses forward, stepping closer until she's almost pressed against him. "It's okay," she says again.

It had all been based on theory.

Back when her powers had first started to manifest, Donnie had juggled his (barely) polite disinterest in all things spiritual with his barely-reined-in interest in all things to do with _her_ , and it hadn't been until the Kraang had gotten ahold of her, and everything that happened afterwards, that he'd really taken notice. Now that there was physical, visible evidence of what she could do, there was something for Donnie to work with. He theorised that her empathy could go both ways — what April could feel, April could _make others_ feel. If April could sense outward intention, she could go in and _steal_ inward intention. She could steal _information_.

She could be a _spy_.

A spy that could blow things up with her brain, but still, a spy, and when she had broached the topic — _"what, you mean I could be in your head? Finding out all your dark, dirty secrets?"_ — Donnie had laughed nervously, cleared this throat and changed the subject.

But Donnie's theories were always sound. Crazy, a lot of the times, but he'd never been wrong.

She'd just never wanted to put his theories to the test like _this_.

This time, when she walks towards Donnie, she tunes everything out except for her and for him, focusing on Donnie and sending forward _trust_ , and _affection_. Donnie needs to know that he's safe with her, that he can trust her, that he can let her in.

She's met with a barrage of white noise. It's weaker now that he's alone, and it's not as strong. There isn't as much intent, either — keeping her out this time isn't an act of malice but of something else.

April builds on the tight knot in her chest, the one that's two nights old and full of her exhaustion and her grief, and she draws it up until it lumps in her throat, and makes her nose prickle and sting, and she sends it forward in a long, constant stream — Donnie is her friend, Donnie is important, Donnie is safe with her, she _loves_ him even if she's not sure if it's in the way she knows he wants, he _saved_ her and now it's her turn to save _him_ —

When she opens her eyes again, Donnie has leaned forward, tilting his forehead towards her. There's none of Donnie's warm longing in the gesture, but what there is is a lack of resistance. The white noise in his head is quieting down.

"Hey, Donnie," she murmurs, sliding her hands up his face.

Her thumb smoothes gently against the thin pale scratches clustered on his left cheekbone, left over from Slash and almost healed completely. Under her fingertips, Donnie's temples pulse as his jaw works, teeth clenching and unclenching at the intrusion into his personal space. April closes her eyes, looking for that fold in the corner of Donnie's mind that she can pull back and slide through.

Piece by piece, the kitchen falls away; the oven, the fridge, the table, Casey, Donnie—

And then she's gone too.

* * *

 **tbc.**


	8. Part 8

I'm so sorry for the delay on this chapter! I hope it's worth the wait! thank you to everyone who has been following this story so far; it means a lot to me!

tmnt is property of Viacom.

 _in this chapter:_ April does the thing.

* * *

 **Birth of Serpents  
part 8**

* * *

Of all the things April expects the inside of Donnie's head to be like (computer chips; space-age chemistry labs; an old, dusty library full of books and facts and knowledge and a beaten, comfortable leather couch with a turtle's shape worn into one side), it's not this. It's not New York City, _her_ New York, right down to the potholes in the street and the graffiti on the walls. The only thing missing from it is Donnie himself.

April stands in the shadows between two streetlights, closes her eyes, and listens to the silence. There are no people in Donnie's New York; the stores are closed, and the lights are out. The air is just this side of too cold, and there's a low, lingering _loneliness_ , too, a hollow ache in her chest. She expands her mind, looking for the familiar, warm thread of Donatello's mind in the darkness; something to anchor herself here, and to him, but it slides from her grip as soon as she finds it, skittering away into the night.

If Donnie is here, he doesn't want to be found. And if he doesn't want to be found, then maybe he doesn't want to be _caught_.

But he's left a trail behind him, down the street and towards an alley. It's an alley April recognises: the one that she usually takes to her favourite manhole, the one that's a block away from the lair but four tunnels over. It's new enough that the metal doesn't shine through rust as a hint that more people use it than just the city workers, and so old that everyone else barely notices it. The street it's on is quiet enough, but busy enough, that nobody notices — or cares — when a teenage girl slips into an alley, sometimes with a boy, sometimes not, and then never comes out.

Outside her alley, Donnie's mind vanishes. The passage is blocked off, covered by a rusted old truck. It's another four blocks to the next one, and then another eight tunnels to get to the lair, through the worst of the sewers. Bending low to look between the truck's wheels, April can see a pile of old crates stacked over the manhole, the pile higher than she can see. There's no way into the lair here, and there's no way whatever is down there is getting out.

Donnie wouldn't bring her all this way unless it _meant something_ , she tells herself. If Donnie is here, if Donnie is leading her around his own head, he's trying to tell her something.

The manhole is blocked, the alley closed off, and Donnie is still out in his own night.

 _The lair isn't safe,_ Donnie is trying to say. _Don't come down, April. Stay safe. Stay away._

"Okay, Donnie," April says, chafing her hands against her arms, her skin pricking with goosebumps. "So where are you?"

Donnie doesn't answer. April didn't expect him to, but when he _doesn't_ , it somehow hurts more.

A block later, something shifts in the shadows. A roil of scales glimmers in the light, and the sound of something dragging itself along the sidewalk scrapes along the air; April spins, expecting to see Donnie behind her — an _evil_ Donnie, maybe, with his green eyes and sharp, sharp teeth — but there's _nothing_.

When she reaches her building, it's barricaded, no window unbarred, and the door blocked as best as somebody could — a dumpster dragged in front of the stoop with its wheels snapped off. The lights are on in her apartment. Someone is home, but whoever is in there doesn't want visitors.

April is not a visitor. Her key, in her back pocket, starts to feel hot.

If the lair isn't safe for Donnie, she realises, then he would go somewhere else, somewhere important, somewhere he needed to protect.

Her heart twists in her chest. _Dammit, Donnie._ She hops the dumpster and stomps up her stoop. Donnie and his sense of duty, and his loyalty, and his almost-overbearing need to make sure that she's _safe_.

Her stomach chills to ice the instant she sticks her key in her lock. She feels the soft, gentle flicker of a snake's tongue against her neck, careful and deliberate, as something hisses: _get out._

 _Get out._

April whirls around, her hand already reaching for her tessen, but _again_ , there's nothing behind her but _air_. She keeps her weapon out, this time, scanning her surroundings carefully before she turns back to the door, and then again, the soft hiss comes back, rasping at her back: _get OUT._

At the end of her block, the streetlight flickers once, then silently dies.

 _Get. OUT_.

One by one, the other streetlights go out. Shadows rise up like an army, dark forms that are not human or turtle or snake, but something else — all of them twisting and writhing together, and all of them watching her through bright green eyes, and all of them _hissing_ :

 _GET OUTGETOUT GETOUT GETOUTGETOUTGETOUTGETOUT_

The last light fades, and the streets are dark, and all April can see are green eyes rushing at her as the ground comes up behind her—

Then, blue.

And then, there's _nothing_.

* * *

"Red!" Casey yells, his hands clutching her shoulders, and April comes to as he's hauling her away from Donnie — Donnie who stands there, not blinking, barely breathing.

Just watching.

* * *

"Something's in Donnie's head," April says, not long after. Casey shoves a mug of coffee at her and watches until she wraps her fingers around it — he doesn't know all the details of April's weird mind thing, but he can at least shut up and listen while she processes it. Her hands are shaking.

When he'd pulled her away from Donnie, she'd started to _hiss_.

"I don't— I don't know what it is, but it's there. It's…" She shivers. "It's not good. We have to tell Splinter."

"Okay," Casey agrees. "And then what? Can you get it _out_ of his head?"

"I don't know." April leans forward until her chin is basically _in_ the coffee mug, and stares into the air. "If I could, where would it even go?" Her brows scrunch together at the thought, and Casey squeezes his fists together to stop himself from leaning over to rub away the lines there with his thumb. This isn't his wheelhouse. Casey wants enemies he can see, the ones he can feel at the end of a stick. That something is just slithering around in Donnie's head feels like cheating. "Whatever's in there is in control, so if it goes into _me_ …"

"Yeah, no." Casey flattens his hand against the worktop. "That's not happening."

"What's not happening?" Karai asks, from the archway into the kitchen.

* * *

"Well?" Karai prompts. She glances between O'Neil and Casey, both of whom couldn't look more guilty if they tried, and then she folds her arms. "Is that for me?" she asks, glancing at the blue mug cooling on the counter and taking it without waiting. It's not tea, but it'll do. She watches through the steam as O'Neil non-verbally tells Casey to _shut up_ and glances once to Donatello. He's standing still in the corner, blank-faced, his shell backed up against the countertop.

Nobody says anything.

She takes another sip of coffee and forces it down. "I spoke to Leo," she says, as lightly as she can, and watches to see how the others react.

"Yeah?" Casey asks, leaning back. "How'd that work out for you? He ask for some fava beans?"

Karai doesn't get the reference, but O'Neil punches Casey in the arm. "What did you talk to him about?" O'Neil asks, looking back to Karai.

Karai nods at Donnie. He hasn't moved since she walked in the room, and he's still staring at her, cold and unreadable. Karai wants to look away, but she knows that she can't. Donnie is dangerous. So Leo gave her him to work with — that doesn't make him safe, and it doesn't mean Donnie will suddenly wake up, as though this was all just a bad dream. The mutation still happened, and Donnie's still part-snake. He's still one of _them_. That makes him a sleeper agent. And with him the way he is — non-verbal, still frighteningly still — that makes him a threat.

She needs him to be a threat. She just needs him to be a threat to someone other than her.

"What _about_ Donnie?" O'Neil asks.

"Leo agreed to a trade. We get Donatello, and he gets to finish the retromutagen."

"And what does Leo get in return?" O'Neil is deliberately slow, careful with every word, and Karai doesn't want to answer. Just because it's not a betrayal in fact doesn't mean it's not a betrayal in words. Words are worse than action, sometimes. Actions can be fixed, plans can change, but words, once spoken, are out forever, even the ones that turn into thorns and tear at the throat. Karai is still betraying her father.

"It doesn't matter," she eventually says. "Because he won't get it."

O'Neil sizes Karai up, her blue eyes narrow and her face tight. "Yeah," she says. "He won't. Because this plan isn't happening. Donnie can't even go in the lab with Leo and Mikey there; what, is he supposed to make it here in the kitchen?"

Casey clears his throat. "…just go with it, okay, April? Karai's… she's got a plan."

Surprise flickers across O'Neil's face; Casey called her _April_ , not _Red_ , Karai notes, so it must be serious. O'Neil opens her mouth, closing it once, then tries again: "You _knew_ about this?"

"I didn't know we were handing Leo the talking stick just yet," He raises his hands in defence, but looks guilty as sin. "…but yeah, I knew about the Donnie thing."

"Since when?"

"Yesterday. We talked to the creep and Karai made a deal."

Technically, Casey did nothing aside from wait on the street, but if he wants to take part of the blame, then Karai isn't going to stop him.

"'The creep'? Which creep?"

Casey shifts, so Karai fills in what he can't. "Baxter Stockman."

"Baxter— you mean you _already_ —!?" O'Neil wrenches away from Casey, backing up towards where Donatello is _still_ staring, _still_ watching, and Karai wonders, too late, if having this conversation near him was a good idea at all, now that she knows what she knows.

It is, she thinks, because they don't know everything.

" _Enough_." Karai slams her mug down on the kitchen island, cutting O'Neil off before she can interrupt. She's not in the Foot anymore, she can't use her troops to get O'Neil back into line, and now, there's far too much at stake and they _need to listen_. "About the turtles," she says, and rails over O'Neil with, "they're a hivemind."

O'Neil's hand jerks abortively towards her temple, and then stops. Casey, too, looks paler than he should. Karai's stomach twists, a thin, tight little choke — she wasn't the only one keeping secrets, but she should have been, and, more importantly, she should have expected that she wasn't.

Too late now.

 _Careless, Karai,_ says the Shredder in the back of her head, and for that one moment she can feel him behind her, a looming presence. Once it offered her protection, and guidance, and power, and now—

He should repulse her. He _does_ repulse her. But not every lesson he taught her was the wrong one. She should have seen this coming. O'Neil is not as stupid as she looks.

"I spoke to Leo," Karai says, when it's been quiet a moment too long. "I offered them a deal. And when he talked to Mikey, he didn't."

"Didn't what?"

"Talk. Not with his voice."

O'Neil's hand drifts up again, curling into a half-fist before she cups her own ear.

"Red, c'mon." Casey's voice is calm, placating, _pleading_ , almost. Whatever it is O'Neil isn't telling Karai, Casey seems to think it's something Karai should know.

Karai is inclined to agree. "Look," she says, trying for patience and flattening her hands on the concrete block. "Maybe we should have _all_ been a little more honest from the start. Maybe _some_ of us should have done what they were told. But Donnie? He's the smart one."

"And then what? We go crawling to the Kraang if things go wrong? Or they have to hide for the rest of their lives because they can't even go outside anymore, just in case _your dad_ is waiting with a super-soaker."

The words snarl out of her before Karai even knows she wants to say them: " _He is not my father_."

"You keep saying that." O'Neil's voice is spiteful, _nasty_. "But all I hear in this plan is you trying to sell Splinter out, and put the turtles in danger. Sounds a lot like Shredder to me."

Karai reels herself back in. "We're _all_ in danger right now, O'Neil. It's standing right next to you." Donatello doesn't even try to defend himself. She jabs a finger in his direction. " _He_. Is part of a _hivemind_. They _let him go_. Do you really think your little boyfriend over there is going to just snap out of it?"

O'Neil ignores the snipe — it'd be commendable if she was ignoring it out of discipline, instead of stubbornness. "There have to be better options," she says.

"There _aren't_." Karai folds her arms. "This is our only shot."

" _You don't know that_. Donnie's still in there, I _know_ it, I—"

O'Neil cuts herself off. It's not the normal, over-emotional cutting-off Karai expected, or would expect, from someone like her. O'Neil is cutting herself off because there's something she doesn't want Karai to know about. Karai leans over the concrete, making sure that she can look O'Neil in the eyes. "You what?" she asks. "Did Donnie suddenly fix himself and tell you all about it?"

O'Neil scowls, her cheeks two hot points of red in a pale face. Her eyes are dark and almost-bruised from lack of sleep — she looks haggard, and exhausted, and Karai just wants to be _mean_ , just enough, so that O'Neil will blow her top and tell her everything. It's a tactic that usually works; she's watched Shredder do it a hundred times before, on cocksure new recruits until they submit to their master, and their punishment. "Or is this just another of the things that make April O'Neil so _special_?"

O'Neil snarls, and takes one step forward. Karai wants her to — would love nothing more than to smack the answer out of her, but Casey pulls O'Neil back with a hand on her shoulder. Karai swallows her disappointment, settling instead for raising an eyebrow as O'Neil carries on her tantrum: "This is not happening," she says. "We're not giving _the Foot_ the one thing they need to _literally murder_ the turtles. We'll figure something else out."

Karai sighs, loud and deliberate. "We don't have time for that. Stockman's there, he's willing and more importantly, he's _weak_. He's a weak, _spineless_ coward and usually when you want someone to do what you tell them to, that's a good thing." O'Neil doesn't need to talk for Karai to know exactly what she thinks, and Karai is about as disgusted with her and her Nadeshiko routine as O'Neil seems to be with Karai. But there's a fundamental, fatal misunderstanding here. "You want to be a kunoichi?" Karai asks.

O'Neil scowls. "I _am_ a kunoichi."

"Playing at martial arts and sneaking around doesn't make you a ninja. If you want to be a real kunoichi, then you'll realise that sometimes, we have to do the _dirty_ work."

"Like selling people out? What happened to your _honour_ , Karai?"

Karai pulls herself up. There's so much anger in O'Neil now that she can feel it, like a warped type of ki that fills the kitchen air and poisons the atmosphere. It twists and holds itself taut, straining and pulling, and Karai needs to, and knows how to, break it. "There's more honour in this than being a little white girl playing _dress-up_."

 _Snap_.

O'Neil moves; she's too slow, sleeplessness and stupidity and stress dragging her feet and arms. Karai doesn't even have to move her feet to dodge the first strike. She clocks the fastest way to end this fight even before O'Neil moves in for her second hit, but before she's even closed her fist, Casey ducks in.

She'd almost forgotten about him — but he isn't coming at her. Casey drops low, his shoulder meeting O'Neil's gut as he hauls her into a fireman's lift. "Whoa-ho, okay, uh, Red, can we talk for a second? Great, _thanks_ ," Casey says. It's a move that Karai almost wants to be impressed with. Casey — like Karai — isn't exactly _built_ , but as he scooped O'Neil up and dumped her over his shoulder, the muscles in his arms tensed, his back strained. It's not the time, but it wasn't a terrible view.

He doesn't even look at Karai as he leaves the kitchen.

Which leaves her alone with Donatello.

He still hasn't moved.

* * *

" _You need to tell Karai_ ," Casey says, as soon as he puts April back on her feet. He's dragged her out to the pit, far enough away from the kitchen so that Karai won't overhear, and he ducks down, making sure he's in April's face so that she _knows_.

But he's only there for a moment before April shoves hard against his shoulders and he sways back, half self-preservation, half the fact that April might be exhausted but she's a) pissed off and b) Splinter's student. She comes at him again, shoving him with her palms flat on his chest and then backs off, her hands curling into a fighting stance.

Casey doesn't want to fight.

What he wants is—

"You need to _get off my back_ ," April snarls.

—is not this.

"You think _I_ want this?" Casey clenches a fist. "I don't. But if the Overbite Wonder in there's got something _in his head_ , you don't think that's something we should, oh, I dunno, _tell people_?"

"And then what?" April's voice is a whip crack, and Casey glances towards the kitchen despite himself — yeah, he wants April to tell everybody about the weird shit she's seen, about the weird shit she's had done to her, but he can't do it for her.

For one, it's not his thing to tell.

For two, she would never, ever forgive him.

But he's so tired of keeping secrets from the people who need to know them.

"'Then what' what?" he asks, instead.

April straightens, looking down her nose at him even though she's like, 5'1, and when she speaks again, she uses the same voice she used back when Casey was just a dumb jock to her, nothing more than a way for her to boost her grades: "We already know that something's wrong with Donnie. Then what? Should I go check on Raph? Or Mikey? Or hey, why don't I go take a look around Leo's head?"

"I didn't say do that."

"Except," she railroads over him, "that it's _probably Leo anyway_. And what if they get hold of _me_?" she asks. "You said—"

And he'd meant it — she'd hissed, low and quiet and slow, her eyes thinning until he'd dragged her away. "Yeah," he says, "but they _didn't_ , and they _won't_. And — what, you think that's what Karai wants?"

"I didn't say that."

"No, but you're thinking it."

"No I'm not!"

"Yeah? Prove it. Go tell her what's in there. Go tell her what you can _do_." He counts them off on his fingers, one by one, his whole arm shaking as he goes from thumb to pointer to middle finger. "Go tell her how you tracked down the turtles, and can read everyone's minds, and—"

"That's not what I can do!" April snaps, but he's on a roll, and rolls right over her.

"—can go walking in Donnie's head."

"Because you don't know her like I do. Karai is _lying_. That's what she _does_."

"Yeah, well as far as I can see, you two aren't that different," Casey hisses, jabbing a finger at her. "You got weird Kraang shit when you were a baby, she got weird Foot stuff. You're pissed off about this, _she's_ pissed off about this. You wanna fix the turtles, _she_ wants to fix the turtles. I don't get why you two can't just _get over it_ and work together on this. Are you gonna spend the rest of your life pissed off at her? Or— what, do you want me to pass messages the whole time?"

"Casey—" She looks away, then gasps, her hand covering her mouth.

Wrapped up in bandages and dressings, and lit on one side from the warm light of the kitchen, Donnie looks kinda pathetic. And he's a ninja, but Casey knows from Raph that — and Raph _loves_ his brothers, and only Raph is allowed to talk shit about his brothers — Donnie, with his big gangly feet and skyscraper legs, isn't as stealthy as he should be, sometimes.

But he's still there, and nobody noticed him.

From behind him, Karai slinks out of the kitchen and shrugs, all _what-can-you-do_. "I turned around to get the sugar. Looks like we need to keep a closer eye on him."

Donnie doesn't say anything. Just looks around the lair, green eyes squinting through the dark. His hands are flat at his sides; he doesn't look like a threat, which, of course, means that he's even more of a threat than Casey has ever seen him.

He should volunteer. But also, he's kind of done his fair share of Donnie Duty tonight by showering him off, and also, he's _beat_.

Then April steps up. "You two should sleep. I can watch Donnie."

Before Casey's gut can twist into jealousy, Karai cuts in, all smooth: "I don't think that will be necessary. I can handle this."

April draws herself up, trying to look like an asshole, and Casey can just see every asshole remark that April wants to say, all about how _sure, Karai can totally handle it, because that's why Donnie managed to sneak out of the smallest room in the lair without her seeing it_.

But then she just… doesn't. "Fine," she snaps, then turns on her heel and marches off back to bed. Casey winces when her door slams, echoing through the lair.

"You sure you'll be okay?" Casey asks. He doesn't particularly want to stay up with Donnie either, not when he's got Raph to deal with, and not when he's working on about an hour's sleep, but he figures he should offer.

Karai just shrugs. "I've had worse nights," she says. "Besides," she adds, jerking her head towards Donnie, "I figure it's family bonding time."

She reaches out to take Donnie's wrist, and immediately, he snatches it away. Casey tenses, but that's all Donnie does; the next time Karai does it, she puts her hand on his elbow instead, her thumb in the hollow, and she walks him back towards the kitchen.

Casey watches them go, guilt knotting in his gut. He should offer to help. He should do _something_ that isn't leaving Karai alone with Donnie, and whatever, or whoever, is in his head.

But Karai — yeah, she looks beat, but she's nowhere near the level of total wipeout that he and April are approaching. As much as Casey hates to admit it, he's not sure that if Donnie turned again, he'd be any use other than a nice, chewable distraction. Karai still looks like she could go a couple of rounds without breaking a sweat. She can't be any older than Casey is himself, and a dark little curl in the back of his gut wonders — exactly how did Karai get to be as good as she is? _Probably got an owl_ , he thinks, from _Uncle Shredder's Academy of Murder and Mutation_.

He snorts quietly to himself and shuffles quietly down the corridor.

Outside Donnie's room, Casey waits for a second, trying to hear anything from April at all, his gut jumping. But there's nothing. Sighing, he turns on his heel and shoves into Raph's room.

All he wants to do now, is just pass out for about fifteen hours, and wake up in the morning and maybe tomorrow it'll all be a better day. Maybe tomorrow Donnie will have figured out how not to be a murder-snake in that big brain of his, and already fixed it in between chowing down on Splinter's leg and making his first batch of coffee.

Maybe tomorrow, Casey can take Raph for a walk in the sewers, and come back, eat breakfast, and go take Shredder out.

Yeah right.

He flops heavily onto Raph's mattress, kicking off his sneakers, and Raph slowly slithers out from under the bed, his mouth poofed up at the sides around a rat he has lovingly murdered. Casey stares — what the hell else can he do? — as Raph presents it at Casey's sock-covered feet, then looks up, with big giant eyes, waiting for praise.

"Yeah, good boy," Casey forces out, unable to not look at the spit-covered, punctured, blood-clotted _dead freaking rat_ dumped on the floor. Then he stretches, and pats one hand against his belly. "But I just ate. It's all—"

Raph snaps it up in his left mouth. It goes down whole.

"—yours."

Raph burps, very quietly, through his right nose. Casey rolls his eyes, shoving his feet under Raph's tiger sheets. Like everything else Raph owns, it's a salvage job, probably snagged from the street or a dumpster after a kid finally discovered Power Rangers, and they're pilling from dealing with scales and shells for however long they've been in the lair. But they're soft, almost too-thin — Casey can see the shadows of Raph's mildewed duvet under where the fabric is lightest and thinnest — and right now, they're _awesome_.

Raph huffs from all three heads.

Casey cracks open one eye.

Raph stares at him, tongues flickering out once, then again as he scoots closer to the bed.

He is literally the biggest dog Casey has ever had.

"Yeah, sure, climb up," Casey sighs, scooting back towards the wall and patting the bed beside him until Raph slinks under the covers, the end of his tail curling around Casey's ankle, and Casey forces himself to not feel weird about it when he can feel Raph's scales catching the hair on his shin.

It's just two friends, going to sleep.

One just happens to be a giant mutant murder-snake.

Except this is also _Raph_ , who takes pride in beating Casey in the _how many days since I showered_ contest (current record: four days, and it's a _tie_ , after Leo and Donnie dragged Raph kicking and screaming into the bathroom, and Casey's dad blocked the front door with all of his big, ex-NHL bulk, and handed Casey a brand-new bottle of Old Spice shower gel, and Casey just took the loss like a man), and is so super-manly he unironically reads Super Princess Polly comic books and punched Casey in the dick the one time he dared to laugh, but even Raph would have to admit that there is something that is really, _really_ gay about snuggling up with your best friend — whether he happens to be a giant snake or not.

Unless he really, really _needs_ to snuggle.

Casey's a big brother. He knows that sometimes, in the middle of the night, when your door opens, and someone tiptoes across your room and gives you the pity-sniffle, you just roll over, lift your blanket up, and prepare for a lot of cuddling and maybe telling a bedtime story or four. That's the rules.

"What's the matter with you, buddy?" Casey asks, even though he doesn't expect an answer. "All the others are back on two legs, why not you?"

Raph shivers.

* * *

 **tbc.**


	9. Part 9

tmnt is property of Viacom.

 _in this chapter:_ movement

* * *

 **Birth of Serpents  
part 9**

* * *

It doesn't really matter how long Casey sleeps: it's not enough. A truck honks loud enough topside that the noise drags Casey awake from what little snoozing he managed in Raph's lumpy old bed, and as soon as he realises where he is, everything else comes crashing down too.

He's in Raph's bed, and Raph is in front of the door, huffing through his three noses, waiting for Casey to stop taking his sweet-ass time and get out of bed.

The cracked old CATS clock on the wall points to twenty after nine.

 _Didn't even get four hours_ , Casey grumps, snagging his jeans from the pile on the floor and jamming his feet roughly through each leg. He doesn't bother to give them the cursory morning sniff — they're gross, he knows that he's in for it when he goes home, his dad standing guard as Casey shuffles around the kitchen in a pair of old sweats and measures out enough detergent to kill every disease known to man, and give them delicate, baby-soft corpses — and he's reaching for his socks and sneakers when Raph huffs again.

"Yeah, I _get it_ ," Casey snaps, then swallows, then grimaces. His tongue tastes like ass, and there's something oily and furry on the sides of his teeth. Bathroom it is, then — at least then he can kinda look like he _tried_ in front of April.

And Karai.

Again, like everything else in the lair, the bathroom is dragged together from both whatever Splinter found here in the first place (there are tiles here that look older than the ones at Bleecker Street), and whatever they've gotten from the street. There's a big claw-foot tub, with a mismatched faucet and a hot-water dispenser made out of dingy yellowed plastic. The toilets are neat, tidy cubicles. The sinks always run cold.

The ice-water on the back of his wrists almost hurts, and when Casey cups the water into his hands and throws it into his face, he imagines for a second that he's at the practise he can't blow off later, on his skates, on the ice, his breath frosting up in front of him.

Ignoring Nick, and how his shoulder always seems to find Casey in a crowd, and focusing on tonight's training instead.

But he's _wiped_. The cold water stops helping after like five seconds and then gets annoying — it drips under his nose and itches, and he's so beat that he feels like his _brain_ is bleeding: a hot, wet trickle that wriggles from under the metal plate all the way down to the back of his neck.

All Casey wants to do is go home after training tonight, crawl into his own bed, and sleep for four days. Or at least a whole night, uninterrupted, waking up in the morning when his sister puts her crappy TV shows on and his dad starts a fresh pot of coffee. April won't be crying across the hall, and Karai isn't having Happy Sibling Time with Donatello, and the turtles aren't all trying to eat their own dad.

Instead, Casey reaches under the sink and snags a spare toothbrush, loading it up with Leo's prissy brand of Extra Whitening Sparkle Smile toothpaste. Some slops off the brush and splatters in the sink, stark against the faded ceramic, and Casey lets himself enjoy it — serves Leo right, for being a _creepy little shit_ ever since this whole thing started.

 _You're stalling, dickbreath_ , Raph doesn't say, breathing slowly, when Casey spits into the sink.

 _Yeah_ , Casey thinks, swallowing a mouthful of leftover toothpaste foam and cheap bristles. _I know_. His teeth are clean, his face is— better, and there's a crusty old roll-on deodorant under the sink too that he snags, and rolls in his palm until something worth using comes out.

There's just one thing left before he's _really_ stalling.

"Okay, Raph," he says when that's done, to the needy snake that's still clinging to him like a lonely hula-hoop. "You're _really_ gonna have to get off of me for this."

When Casey's finished making a big brown snake of his own ( _god, you're disgusting_ , he can hear Raph not say, even though Raph sits in his own farts like he's just tooted out potpourri), he kicks the cubicle door closed and washes his hands before shoving away from the sink, already tensing for the weight of Raph to come curling around his legs.

Raph doesn't come.

Instead, when Casey turns around, his gut drops, horror rising into his throat and stopping there.

Raph is staring at him.

 _Raph_.

With his big, meaty turtle head. The rest of his body is twisting, _writhing_ , bones snapping and skin bunching and stretching. The two heads where his hands should be are swollen: fat, bulging heads, all four eyes popping and leaving bloody smears on his hands. The teeth sink into Raph's skin.

"Oh shit," Casey breathes, backing up. "Oh shit, oh shit, oh _shit_ —"

He reaches for the mop next to the sink. The wood is soft and worn, but it's all Casey has. "Raph," he begins, feeling a cold sweat start pricking his skin; his heart is in his throat and this is it, this is when Raph finally goes crazy, and April and Karai are going to find Raph fat and asleep in the shower, and he will burp up Casey's bandana and that's the end of Casey's not-metal-enough life.

 _No_.

He's not going out like this. He and Raph are going to be just fine, and when Raph is all better, Casey is going to show Raph the photos he took on his phone last night when Raph was snuggling closer in his sleep, and Raph is going to punch him, and Casey will laugh.

"Raph," he tries again, his voice shaking, waiting for Raph to make the first move. "Raph, c'mon, talk to me."

" _Case_ —" Raph says, face creased, eyes scrunching, his sharp teeth gritting together like he's straining; in pain; trying to force something out before it gets too much. " _Case_ —"

Then Raph chokes, something warping the shape of his throat and pushing his Adam's apple out by inches. His eyes bulge. He splutters something else, and then a snake's tongue bursts out of his mouth, lashing at the air.

He hisses.

It's _feral_.

Raph's face collapses in on itself, and the snake returns.

Raph's whole body blurs back into a long, lithe form and he rises up, mouths wide open, spit misting the air.

He throws himself at Casey, snuggling desperately again. He jams his big snake snout right into Casey's armpit, and then, like Casey bothering to make an effort is the worst thing he could ever have done, he sneezes a lungful of crusty deodorant stink right back onto Casey's shirt. "Thanks, man," Casey says dryly, trying not to look at the shiny string of snake-snot and focusing on forcing his heart to stop racing. "You really shouldn't have."

* * *

April and Karai are already in the kitchen by the time Casey waddles in. Donnie is sitting on a stool staring mutely at a stack of notebooks on the tabletop.

"Good morning, sunshine," Karai says, over a cup of tea. There's only the tiniest smudge of shadows under her eyes, and it rankles as Casey tries to find a comfortable way to perch on a stool with Raph still demanding cuddles.

"We need to talk," he says instead.

April's head jerks up from where she's been staring through her coffee and she looks even worse than she did last night. _Did you get any sleep, Red? Like, at all?_ he doesn't say, and instead gives Raph a firm shove.

Raph slowly starts to slide down Casey's hips, glaring at Karai all the way until he hits the ground with a soft, heavy _thmp_.

Then he holds up all three heads, and keeps glaring at her over the table.

Casey sighs, patting Raph's biggest head, before boosting himself up onto the concrete block. "Raph changed," he says bluntly, and then finds himself backtracking immediately as soon as April opens her mouth. "Not— all of him. It was like he was trying and then couldn't do it."

"Did he say anything?" April demands, and her face falls when Casey shakes his head.

"I mean, he _tried_ but it was like, my name, and that was it. And then…" He gestures where Raph is still scowling at Karai. "Snake."

The worst thing is, okay, so he's clingy and pouty and oh, yeah, a _snake_ , but it's better than Raph going back to the lab where Leo's trying to found a new Village of the Damned.

Better for Raph to be a snake than one of Them.

In fact, it's worse than that, Casey realises, when April sighs and turns away. April said that _something_ — some _one_ — was in Donnie's head, trying to come after her. The same thing must be trying to get into Raph's head, dragging him down.

But April won't say anything, will she?

He glances once longingly to the cupboard where Donnie keeps the coffee, hoping one of the girls will take the hint, and, when they don't, points to the stack of books on the table instead. "What're those for?"

"These are Donnie's notes," April says, resting her hand on the top notebook like she's swearing an oath. "Karai's giving them to Stockman."

She looks at Donnie, and Casey does the same, waiting for Donnie to do anything, _react_ , start yelling, stamp his foot — but he does _nothing_. April sinks into herself a little more. "We're heading over there tonight," she says. "Donnie's coming with us."

Casey knows the score about Stockman, but he's still a creep with the Foot, so he has to ask, if only so he can do it before April does: "But like, what if Stinkbug decides to just flush Donnie?"

"That's why he's being guarded," Karai replies. "Two of us at any given time," she adds, before Casey can point out — again — that he has to go home.

"Yeah? What about Laurel and Hardy in there?" Casey asks, jerking a thumb towards the lab.

It's not Karai or April who answer. "Leave them."

Casey jolts, looking to one of the gaps in the kitchen wall. Splinter is standing on the steps to the dojo. He doesn't move; Raph's heads have all swivelled towards _rat_ , and Donnie is just staring at his sensei, with a creepy, blank look on his face— except it's not blank, Casey realises, a moment later. It's like he's forcing himself not to care, the same way Casey and his sister force themselves not to care the thirty minutes before Thanksgiving dinner is served when the whole apartment smells of turkey and pie because grandma's waiting on her pills.

Donnie's throat works once.

"Yo, should you even be out here?" Casey asks, waving between Raph and Donnie and not saying how this is kind of like a Big Mac walking past a pack of stray dogs.

Splinter doesn't answer. Instead, he looks over towards the lab, where Leo and Mikey are doing god-knows-what. "Leave them," he says again. Casey rests a hand firmly on the top of Raph's biggest head, then presses down firmer when he feels how Raph is trembling, just a little. Just enough.

It's not a scared type of trembling, either. It's holding back.

"Father," Karai says, pushing her way past April and stopping at the bottom of the stairs. Casey can only look at the back of her head — but there's something in the way her head tilts, the way her shoulders straighten, that makes him feel like there's a conversation going on with nobody talking. He glances to April, but she's looking at Splinter as well.

Nobody is watching Donnie, so when Donnie moves, smashing past April in four long, loping strides that get longer with every step, they all react too late. April cries out, all elbows and hips as she slams into the kitchen units; Karai turns on her heel but Donnie shoves her aside too as he marches towards the dojo steps. Raph hisses in alarm, and that's what makes Casey grab one of the bar stools, smashing it against the table block until he's left with a long wooden leg in his hands. Adrenaline rushes through him — Donnie's an enemy, Donnie's a danger, _Donnie hurt April, Donnie's going to hurt all of them_.

—But then Donnie stops at the bottom of the stairs.

His whole body is rippling, Donnie shifting taller and shorter like the sea turned upside-down, the thick, healing tears in his legs glossy and sore-looking. Casey can hear his own heart pounding in his ears, the drip of the kitchen faucet, how Raph is shivering next to him. Karai drags herself back to her feet and stands in front of the steps, as though daring Donnie to take another step, and across the kitchen, April hauls herself back up too, a horrible mix of shock and devastation on her face.

And Casey gets it. Casey doesn't think Donnie's ever — outside of practise, at least — raised so much as his voice to April.

But right now, Donnie doesn't seem to give a damn about her.

Donnie is still staring at Splinter.

He huffs out a tight breath, his body subsiding again until he's no taller than Casey himself.

"Karai," Splinter says, and glances once at Donnie.

" _Hai_ ," Karai replies, stepping forward and reaching for Donnie's elbow.

* * *

April's bruises are still there when they lead Donnie across the rooftops that evening, pulsing hot and painful under her clothes. She forces herself not to think about it, about how Donnie shoved past her like she was nothing, and how what she felt from him was just a tight, angry need to eat.

She doesn't think about it. That's not who Donnie is. She knows — she's _felt it_ — somewhere in Donnie's head, Donnie is hiding.

She clings to that fragment of knowledge like a shard of glass, digging into the palms of her hands until the skin breaks. What happened in the kitchen wasn't Donnie. Eventually, she'll get through to him, or he'll come back to her; they'll all get through this. They always do.

The rooftops are tacky under her boots as she runs, and April narrows her eyes as Donnie and Karai run ahead of her. Karai leads and guides at the same time, slipping in and out of shadows, and Donnie silently follows her.

The mutation hasn't affected his athletic skill; Donnie is still a ninja, but his landings are slower, smoother, his knees curving into a slick roll before he gets to his feet without using his hands. His whole centre of gravity has changed, and April can't not watch as the muscles bunch and twist in new ways under his skin. Donnie's body has always been interesting — how could it not? — but now there's something new to that; his big feet quieter, his limbs not quite as gangly and awkward.

"Donnie," April says, turning to him when they stop on the rooftop opposite the church. His green eyes flick down to her, but he doesn't say anything else, so April pushes ahead. "You don't have to do this."

"Yes he does," Karai says.

" _No_ , he _doesn't_." April turns back to Donnie, still looking at her, still not _looking_ at her. "You don't have to do this," she says again, her eyes flicking between Donnie's. Donnie was in there somewhere, Donnie was _hiding_ in there, somewhere, no matter what he did before.

Donnie doesn't say a word.

"O'Neil," Karai prompts. "Let's go."

The creep into the church ruins is over sooner than April would have thought, and maybe that's for the best — the faster they're in, the quicker this is over with, and the less chance there is of them being caught by the rest of the Foot. They slip into Stockman's new lab, charred and thrown together and already stinking of refuse and waste, and the door locks behind them.

April can't help the chill that runs down her spine.

Donnie takes four steps forward, looking around at the laboratory. April presses her lips together, reaching out with her mind to Donnie — a Donnie in a lab, _any_ lab, should be excited, or curious, or scornful ( _this is what they're using for_ science? Or _how many beakers can I carry home?_ or _oh great, animal testing, just what I wanted to see on a Saturday night_ ).

But as quickly as she senses it — the tiniest part of everything that should be Donnie — it's torn away from her, and locked down. There's nothing else.

Not even the soft flicker of a tongue on the back of her neck.

Karai clears her throat. "Stockman," she says. "We're here."

Something buzzes overheard.

"Watch the doors," Karai says, turning back to April and tossing her head towards the heavy steel behind them. She leaves before April can snap anything back, feet padding silently across the laboratory floor until she's at Donnie's side. Her hand cups Donnie's bare elbow, thumb gently resting against the pressure-point to keep him still. "We're here," she says again, tilting her head to the air.

Baxter Stockman swoops down from his nest, and Donnie rears forward, his left hand blurring into a pair of jaws that snap at Stockman's face. Stockman shrieks in fright, and flies out of reach. " _Rude_ ," he spits, from on high.

Donnie hisses furiously, the sound burrowing into his throat until it's a wildcat's roar, spit flying from his throat and his canines glinting in the light. His body starts to twist — he's so much longer as a snake, so much more deadly— "Donnie, stop!" April yells, and he turns one head towards her.

Then another.

Then another.

In this half-transformation, neither turtle nor snake, Donnie looks monstrous. His legs are longer, lither, and they ripple as he takes a step forward, like twin serpents. His hands are hissing heads, his eyes are green and much too far apart, the slit pupils narrowed to black flecks. His mouth opens, fangs bright, and he's hungry so _hungry_

Her head is full of hissing.

"Donnie," April says softly, taking one step forward, approaching him the same way she would a wounded cat — cautiously, and gently. "Stop."

Donnie snarls, but backs down obediently, allowing Karai's hand to rest on his forearm as his body melts back to the way it should be; hands and feet, instead of faces and serpents.

Stockman flies back down, and Donnie hisses softly, but this time, he stands still.

Karai hands over one of Donnie's most precious notebooks, the one with the retromutagen formulae, and April's stomach rolls as Stockman gets his filthy, dirty hands all over it.

This has to be done, she tells herself. The sooner it's over, the sooner Donnie is back, the sooner his _brothers_ are back, and this whole thing is just a bad dream.

 _How many times have I told myself that lately_ , April thinks, wryly.

The answer is _a lot_.

She takes a deep breath, and listens, feeling out the air in the room. There's Karai, tightly-wound and duplicitous and ready; there's Stockman, fretful and fussy and nervous. There are other people too — distant, far away from the lab, but dark enough to be recognisable. Shredder may not be home, but that doesn't mean his underlings aren't. Somewhere, Xever is lazily swimming in a water-feature, his thoughts calm and relaxed, and some ashigaru-sha are running through kata with Rahzar.

April misses Casey at that moment, furiously, and angrily. Casey who left on the run over here to go back to his normal life — to go to play hockey, to eat dinner with his dad and little sister, to keep his cover story going. April has never had siblings, not until the turtles came along, but what she does know is a different kind of gnawing, aching loneliness — missing something she has never had. Watching the turtles, and how even when they'd screamed at each-other they were never without each-other, watching how Casey's face softened whenever he talked about his sister; April had never had anybody like that, just distant cousins, and half-formed friends.

Of course her thoughts focus on Karai. It's not hard to make the comparison: two girls, both lonely, only children, both with no mother to speak of. April can still remember her mom, the warm tumble of sandy-blonde hair and soppy kisses and the smell of the earth from the flowerbeds around the farmhouse. Karai had none of that. Even in April's darkest moments, the times she _hates_ Karai for everything she's done, she can still feel pity, and she can still feel covetous. The turtles were hers first; that stable, steady love was _hers_ , and the thought of sharing it with someone else, someone who might even be more eligible for it than she is, makes her heart rebel.

 _What would you do, Mom?_ she thinks, watching Karai chivvy Donatello — Karai's _brother_ — into position, handing him notes and sharply telling Stockman to not get too close.

There isn't an answer. She hadn't expected one, not really. But it would have been nice.

* * *

Raphael has been confined to his bedroom.

Splinter never approved of his sons having locks on their doors, and so the door is barricaded with a mess of chairs and blunt weapons from the dojo. Leonardo and Michelangelo remain in Donatello's lab — an act of necessity, and Splinter is thankful that neither of them have gone exploring. It is an unfortunate fact that, though a diligent scientist, Donatello is often lax in his security methods, resulting in fires, and explosions, and mutating brothers.

All of it comes from Donatello's need to _know_ , as well as his need to _protect_. Splinter may not agree with his son's methods, preferring that Donatello keep to the teachings he has been raised with — but perhaps, in his own way, Donatello is not wrong. Donatello wants to keep his family safe, and safe he keeps them, with all manner of strange creations.

The idea of another son losing himself, especially his bright, gentle boy, does not sit well, but the thought of what could happen should Leonardo get ahold of some of Donatello's more dangerous toys is worse. "How's your foot, sensei?" Leonardo asks as Splinter approaches. His voice is clear, no trace of the gravel caused by the sedatives, and in his mind's eye, Splinter can see his son, mouth pressed against the crack where the door meets the wall, waiting for a response.

Splinter does not reply, does not want to listen to whatever cruel words Leonardo says in reply — if he says that the bite troubles him, Leonardo could gloat; if he says that it is healing, Leonardo could say what a pity it is, or how fortunate it is that Splinter is healthy prey.

As it is, Leonardo speaks anyway: "I hope you can still run."

Something snickers behind the door.

He sits, and breathes, acknowledging and letting go each time his heart clenches in an iron-gauntleted fist; his sons are not lost, merely waylaid. They will be cured, and they will come home to him. His daughter's plan can only be allowed to succeed. He is a hopeful man, and a faithful man.

Hope is something that he knows well, hope is something that has kept him going for seventeen years, through bitter winters and near-misses, and now through this war that has reached out of the past and tried to drag his sons down with it.

"Where's Karai?"

A breath is a river, rolling over stones and flowing out to the sea.

"She's not here," Leonardo says. "Where is she?"

A breath comes rolling in like the tide, soaking into the sand and depositing shells.

" _Rat_ ," Leonardo snarls, and slams his fist against the door. "Where is she?"

When his son was using the snake's body, it was somehow easier to bear than this. Now, this creature wears Leonardo's face, but it is clear that it is not his son in control. "She is not here," Splinter replies.

Leonardo scoffs. "I know _that_ ," he says, and Splinter cannot help his immediate reaction to such insolence — the urge to discipline rises up, his tongue and his hands waiting to deal blows and words.

But this is not his son. His sons have been taught discipline; his sons _know_. This is an enemy in their home, and he must be treated as such; drawn out, like a poison from a wound, and then destroyed.

"I want to talk to her," Leonardo says.

Splinter's first reaction, and his second, is an outright refusal — this is his _daughter_ Leonardo is talking about, and Splinter has no intention of handing her over. But his third is the knowledge that he has no choice — Miwa is, and always will be, the intermediary in this.

"About what?" he asks. "Perhaps I can pass a message to her."

"Or," Leonardo says, and Splinter's ears pick up the drag of his finger as Leonardo doodles idly against the door. "You could let me talk to her."

"She is not here."

"Then bring her. We just want to _talk_. About our _deal_." He laughs again, short and low. "Did she really think that we'd just _give_ him to her?"

* * *

 **tbc.**


	10. Part 10

tmnt is property of Viacom.

 _in this chapter:_ Karai puts her plan into action.

* * *

 **Birth of Serpents  
part 10**

* * *

April forgets all about her phone until it starts to ring.

The bright, chirpy little melody Donnie programs into literally all his inventions sings out, and April scrabbles for her back pocket. Her dad probably dosed himself asleep, the turtles can't come to the phone right now, and Casey would text, so who's calling?

When she finally drags her t-phone out, the display lights up with a large wedge of cheese, alarm-lights spinning in each corner of the screen.

Her gut drops.

"Sensei," she breathes, then drags her thumb across the screen and pressing the phone to her face. "Master Splinter? What's wrong, is everything okay?"

Across the room, both Karai and Donnie watch her, while Stockman keeps working. Down the line, she hears Splinter hesitate, and the faint click of his claws as he holds the receiver closer. Something is wrong, April feels it in her bones. "Do you need us to come back?" she asks.

" _No_ ," Splinter says. It's the warm, accented _no, of course not_ 'no', rather than _no, because I am unable to say yes._ There's something else in his voice, too, but April can't read him by voice alone. " _May I speak with Karai?_ "

April ignores the twist under her heart. Karai doesn't have her own phone yet — at least not one patched into Donnie's network. It makes sense Splinter would call _her_ if he needs to speak to _Karai_. "It's for you," she says, holding her hand out and waiting for Karai to clue in. There's a small spark of surprise from Karai as she looks at her, and a thrum of suspicion before that fades into an uncomfortable warmth as Karai realises who would be calling for her.

"Thanks," Karai says, before moving away to take the call.

April tries to keep one ear on the conversation, even though as soon as Karai talks to Splinter she switches immediately back into Japanese. She can pick up on tiny fragments of sentences, but not enough to _understand_. She digs her nails into her palm, and turns her attention back to Donnie, and to Stockman. The turtles never froze her out through language before.

Language isn't going to help her now,. Not to talk to Donnie. Since snapping at Stockman, he's stayed calm and still, and though his eyes have never left Stockman, they're less hungry than they are cold. Maybe it's just because Stockman would be disgusting to eat. Maybe it's because Donnie is biding his time. If Leo has let Donnie go from whatever it was in Donnie's head—

 _Blue eyes come at her, cold and deadly, rushing quickly, quietly through the dark_

—If Leo has gotten out of Donnie's head, out of that empty, quiet New York, is it just Donnie in there, or is there something else? Because Donnie is still a snake. That hasn't changed.

Something _clacks_ across the room, and April jolts out of her thoughts, cutting a glare at where Stockman flits over a dropped petri dish.

Donnie jolts too, then hisses, the sound almost lost beneath the sound of six centrifuges running at once.

It's amazing at what can be done when a scientist is using actual equipment, instead of whatever Donnie managed to throw together from the streets, and with an actual plan, instead of Donnie's months of guesswork. So far, April has spat into three beakers, watched as Baxter Stockman pored over Donnie's notes, and waited, counting off each stage in her head — isolation, reversal, combination.

Meanwhile, Donnie still stands there. April carefully reaches out to him through her mind, but all she can sense from Donnie is the feeling of an empty town.

Is he still hiding there, locked in his version of her apartment? Or now that Leo let him go, is he wandering, looking for a way out?

Is the snake blocking every exit?

Does Donnie need her help?

Her hands itch, remembering the feel of Donnie's jaw against her thumbs.

Would it be worth another shot?

Or would it be an unnecessary distraction while Baxter Stockman flits around from lab table to lab table, a cure in one hand, and Donnie's almost-certain death in the other? She forces the thoughts aside. The sooner Donnie is cured, the sooner this will be over. Across the room, Stockman hovers over a centrifuge, wings blurring in the air.

"How long?" she asks, inwardly wincing at how loud her voice sounds, and how rough.

Baxter Stockman turns, even though April is pretty sure he doesn't need to, with his giant fly-eyes able to see all around him. "A few hourzz," he says, the stink of his breath washing over her even from a distance, worse than opening a dumpster on a summer day.

April casts a look to one of the small windows in this part of the church. A few hours means before sunrise.

It could be over tonight.

* * *

" _Hey sis_."

"Leo," Karai says. Splinter hadn't said much to her — only he was fine, the turtles were fine, and that Leo wanted to talk to her, so he would be passing the cheesephone into the laboratory. There was the scrape of the phone being dragged along the floor, and then Leo breathed slowly down the phone; one breath, two breaths, just enough to drag out the silence. Just enough to set Karai on edge, to get her thinking about what Leo could want.

"I'm guessing this isn't a social call," she says, when Leo says nothing.

Instead, he laughs, low and familiar. " _Just checking up on you, you know how it goes. How's Donnie_?"

Karai glances over to where Donnie is staring at O'Neil. "He's fine. What do you want?"

" _So he's not hungry_?"

Aside from Stockman, Donnie hasn't tried to attack anything. He hasn't tried to _do_ anything. He stands around, going wherever Karai moves him: walk here, stand here, wait here. Oh, his reactions are fine; when something makes a noise, he looks at it, but other than that, Donnie is a walking green mannequin.

More importantly, Karai knows exactly where Leo is going with this, like a brave general, walking straight into an ambush that she's set for him.

Sweet, stupid Leo. Leo and all his brothers.

Karai watches Donatello as she speaks, looking for any shift in movement, or a sign that he's about to snap — and snap O'Neil's head off. "Maybe I'll take him for pizza when we're done," she says, adding an edge to her voice she hopes conveys everything she wants back to Leo: _when we're done_ meaning _when Donnie is cured_ , meaning, _when we're coming for you_. A small little lie, enough to tip Leo's hand.

Sure enough, it works. Leo laughs, and says, " _C'mon, sister. You didn't really think we'd just let him go, did you_?"

Karai quells the leap of victory in her chest before it takes hold. A victory is not a victory until the battle is over — hasn't she learned that by now?

 _Well done, Karai._

"No," she says, making herself sound casual, the way she had back when she and Leo had first met on a rooftop, and in a laboratory; casual and calm in how good she is, and in how easily Leo and his brothers have always allowed themselves to be outplayed. "I didn't. In fact I was counting on it. How hungry do you think he is by now, Leo?"

Even though she knows she's winning here, her chest and blood still run cold in the silence that follows, when Leo, on the other end of the phone, must be processing what it is she's said, and what she's tricked him into. She doesn't need Donatello for the retromutagen. She never has. All she ever needed from Donnie was his notes; with Stockman's wings bent, he'll do whatever it takes, if it means that he can be cured himself.

What she needs from Donnie himself is so much more than just what's left of his brain.

Leo lets out a low, impressed _hm_.

It's not the reaction Karai was expecting. " _So you played us_ ," Leo says, each word dripping down her spine like ice. " _Not bad. Did you tell April yet_?" he asks, like he already knows the answer. He lets Karai's silence answer for her, and lets the silence drag out longer and longer before he lets out a soft laugh. " _Doesn't matter. She'll know._ "

"What is that supposed to mean?"

" _April always knows. How do you think she found us_?"

 _Guesswork. Logic. Sheer dumb luck_.

There's no such thing as luck. Karai has known that ever since she was a little girl. No such thing as luck, and the only higher power was power itself, that man should reach out, seize, and bend it to his will. "You came home by yourself," Karai points out, forcing steel into her voice. "Raph went over to his little boyfriend's place."

" _And Mikey_?" Leo prompts lazily. " _Donnie_?"

Mikey went to where the food was.

Donatello hid himself away, in a lonely, dingy tunnel, where he could lick his wounds and stay out of sight, until April O'Neil tracked him down.

It was too easy. Too simple. That O'Neil would just _find_ Donatello the way she did? Karai should have figured it out then, but back then the mission had been to find them and get them home, and Karai hadn't put too much thought into the _how_ , just that they _did_. But now things start to make sense. All the whispered little conversations between her and Casey, the ways that she had been so sure about things without proof—

Karai knew that there were things that she wasn't being told. Secrets were being kept.

On the other end of the line, Leo makes a low, smug noise that sounds nothing like him. " _Aw, sis. Didn't she tell you what the Kraang did to her_?"

* * *

Through the crack in the door to Donatello's laboratory, Splinter hears Leonardo hang up the phone.

He is laughing again.

But when Splinter looks at his sons, though Leonardo's mouth is moving, his lips and chest moving as sound comes out, and though it is his voice that Splinter hears, there is no smile on his eldest son's face. Instead, standing behind his brother, Michelangelo's mouth is pulled into an ugly, fanged grin.

* * *

Leo's laugh rings in her ears long after the phone call ends.

Even under Karai's anger — at herself, at _O'Neil_ — she can still be impressed; Leo had a card left, on the floor, scuffed and beaten under the table, and he picked it up and he played it, and played it well. How long had he been waiting to drive a wedge right through Karai's makeshift little team? He gave her just enough to make a conclusion, but stopped short of telling her everything. Enough to confirm that April O'Neil was more special than Karai originally thought, more _dangerous_ to her than Karai originally thought, but not enough for her to know how _._

All the little looks and whispers between her and Casey make sense now. He must know, the pair of them deliberately trying to keep Karai out.

But does that mean that they know what Karai's plan is? Casey knows what Karai has _told_ him, same as O'Neil, same as her father. But Karai has been running this with her cards close to her chest — everybody is a liability except for herself.

She swallows. If they know, then it explains why O'Neil has been so dogged in her disobedience, and it means that Karai needs to think of a back-up plan, and fast.

"Stockman," she says, marching over to the lab area. "How much longer?"

"He said a couple hours," O'Neil answers, glancing over to Karai.

"Need a _test_ subject," Stockman buzzes, floating over. He looks longingly at Donatello.

"Yeah, no," Karai says flatly. She cuts a hand across the air to emphasise her point — she can only imagine the false sincerity that would come if something went wrong. Stockman hates the turtles in a way that the Foot don't — they never wronged him by clan or by blood, but by being obnoxious, bullying teenagers, being too full of their own egos. Stockman has no honour, and owes them no honour, in this fight. If it went wrong, if somehow the retromutagen reduced Donatello to a small, plodding box turtle, or a puddle of ooze on the floor, Stockman would say oops, wring his filthy hands, and go about curing himself instead. "We'll find you another."

Stockman huffs, then returns to his microscope.

O'Neil's hand tightens on Donnie's elbow, her pinched face shooting Karai a concerned look.

Karai shrugs. "He's not the only one to mutate twice." She watches the understanding dawn on O'Neil's face, and then follows up with, "Can we talk?"

"Uh, sure," O'Neil replies, gently coaxing Donnie along with her. Donnie resists, pulling his arm back, but it's not to attack — instead, he's scowling at the window. Casey is shimmying through, all legs and arms and sweaty hair.

"Hey," he says, landing gracelessly. "How's it going?"

Stockman mutters something beneath the noise of his wings about how _that'zz not a door_ , and they all ignore him.

"It's going," Karai says bluntly. "O'Neil and I were just about to have a little pow-wow, weren't we? Care to join?"

Casey shrugs, falling in behind them as Karai herds them all away from Stockman, her hand firm on Donnie's elbow. "So there's something we need to talk about," she says. O'Neil looks up at her, like butter wouldn't melt, and Karai schools her expression into one of complete neutrality, waiting and savouring the pause before O'Neil's face _drops_ , knowing that Karai knows almost everything. "Leo told me all about you." Of course it's a lie, but it's one of the best types of lie, with just enough truth attached to it to invoke fear and obedience into the enemy. "I think you need to tell me what you know. Starting with all about how you're the Kraang's pet science experiment."

* * *

Everything goes very, very quiet.

"Oh, shit," Casey breathes, his gut dropping. April's so pale he can see even the lightest freckles along her cheeks, and she swallows what looks like the biggest lump in the world. He wants to reach out to her — at least to show some level of support, but all he can do is say, "Leo told her about your brain-thing?"

Karai's head turns like a whip-crack. "You knew?" Her hand drops to her hip, and if Casey were a lesser man, he would maybe need his brown pants. There aren't enough _oh shits_ in the _world_ to explain Casey's feelings right now. April looks ready to murder him. Karai looks ready to murder them both.

"So, uh. About that," he says again, and then makes a gesture towards April — it's her brain, it's her thing to talk about, and Casey Jones?

Casey Jones is just going to take three steps away.

Karai moves, her whole body turning to April, and she waits.

April's face twists. "I'm part-Kraang," she says, her voice flat. "They took my mom and messed around with me before I was born."

Casey wants to think that Karai feels a little bit of sympathy at that, but if she does, she hides it well. Her face is set into a cold look — the _scary_ kind of cold anger, the one that reminds him of Leo more than anything else. Casey has only seen Leo _really_ angry once, and he doesn't wanna see it again.

"And?" Karai prompts, and just waits for Red to dig the rest of her grave.

"And the Kraang work on a kind of…" April waves her hand vaguely. "ESP. They're sensitive."

"So you've been in my head?"

"No. I can—"

" _Read my mind_?" Karai says, and Casey winces. Red never talks about what the Kraang did to her, or why she is the way she is — all he knows is the few things he's seen April do. And if she was in Donnie's head yesterday, why couldn't she be in Karai's another time?

"I didn't _read_ anybody's mind," April corrects. "Not yours, at least."

"But you can?" Karai presses her lips together into a thin line. She looks like she's replaying every time April's been near her since _ever_.

"I can tell if you're lying. I can—" She looks at Casey, giving him the shittiest look he's ever seen on her face, and he gets it, he does. April likes her powers, but hates how she got them. Casey would too. She chews the words out. "I can sense things. Like intentions, and emotions. But I have to focus. And," she swallows. "I can get into your head, but there has to be contact, and concentration. I can't just— it's not like the movies, okay?"

"Oh, I think this is just like the movies," Karai says. Everything about her screams danger, from the slow, lithe way she straightens her shoulders, to the way she drops her voice as though Baxter Stockman isn't across the room listening to every single word they're saying.

(Casey has no idea how sensitive gross mutant fly-ears are, but given that mutation gives everyone super-mutant-powers in pretty much every way, it wouldn't surprise him if Baxter Stockman was listening to Casey digest the street meat he ate on the way over here.)

April screws up her face into something spiteful and mean: "What's the matter, Karai? Got something to hide?"

"Red, c'mon," Casey tries to say, but his words crash against the brick wall of April's stubbornness. If he had been charge, or the turtles had been in charge, they all would have worked together, April's powers and Karai's strength (and his own awesome); Karai could have held Leo down while April went into his head and kicked the tar out of whatever was in there, not this stupid cold war they've got going.

Karai sneers at April. "I'm not the one keeping secrets here."

Casey swallows his automatic interjection — that's a straight-out lie and they all know it. There's so much that Karai hasn't told them. This whole thing has been a shitstorm of _just trust me_ , from all of them.

Instead, Casey watches Stockman, and how he's suddenly, quickly started filling up a beaker of the retromutagen. There's something about the way he's doing it, looking past the girls and over towards the door, that gives Casey a heavy sense of trepidation — he knows that something is about to happen, but just doesn't know what.

"Hold up," Casey says, creeping closer to the door of the lab, then cuts his hand across the air until April and Karai tune in to what he's trying to say: _shut up, someone's coming_.

Out in the hall, there's the sound of claws on floorboards, and harsh, growled breathing. "So about that test subject." Casey slides his favourite hockey stick out of his pack. The others all go quiet, Karai slipping into position next to Donnie as claws scrape along the outside of the door.

"Hey _Stinkman_ ," Rahzar says, slamming the door open, and then, "what the—" when Casey slams his stick into Rahzar's hip.

Rahzar makes an ugly yelp as his hip cracks, and goes down. "Get him!" Casey yells, as April's tessen goes winging past, all edges and heavy metal, and beans Rahzar in the teeth.

Somewhere in the background, Casey hears Stockman buzzing, and he takes the warning for what it is and grabs April by the elbow, throwing them backwards just as a beaker full of retromutagen comes splashing down onto Rahzar's back.

If mutation is gross, then _retro_ -mutation is grosser. Where the formula hit starts to glow neon-green, creeping over Rahzar's body like a wildfire until his whole body is alight. His pelt ripples and bulges, fur melting off and dripping to the floor. Rahzar doesn't scream. He can't, because the mutation melts his big, bone jaws together. Instead, a noise starts in his throat streaming through his nose until that, too, melts and squashes into his skull, shifting and widening out into something less hammer-horror, more comic-book. Rahzar's left arm swells up like a balloon until it's basically just one giant, spiked fist, his legs shorten and thicken and, when the glow fades, whatever Rahzar used to be looks way too much like the darker sections of deviantArt for Casey's liking.

As soon as it's done, Stockman buzzes around, dragging thick, heavy chains around the big arm and locking Rahzar tightly to the wall.

The room stinks of wet dog, and all Casey can think is, _this is happening to Raph_. This is what happened to Raph, too, only in reverse, and maybe this, with the bones shifting and breaking, is what happens every time Raph tries to shift into what he used to be.

"Casey, are you okay?" Something warm bubbles in his chest when April slips next to him, her hand on his forearm.

"Yeah," he says, swallowing when his voice shakes. "Yeah. I'm good. You?"

April just smiles. "It works," she says, her eyes bright with relief.

There's a thin scratch on her cheek — not enough to bleed, but enough to leave a faint white mark across the freckles, and Casey reaches over, meaning to rub it away with his thumb. A little swell of smugness fills his chest. He can't help it, but he and Donnie give each-other so much shit over the thing they both have for April – sure, Donnie might be part-snake, and all-maniac, but there's nothing in the just-got-mutated rulebook that says Casey can't give him a little bit more shit, just for kicks.

But Donnie's not there.

Donnie's gone.

In the quiet of Stockman's lab, Karai is gone too.

* * *

 **tbc.**


	11. Part 11

tmnt is property of Viacom.

 _in this chapter:_ the beginning of the end. thank you guys, so much, for sticking with this story for so long. we're almost done.

* * *

 **Birth of Serpents  
part 11**

* * *

Donnie hesitates just outside the room, and Karai stops with him.

Tension ripples through his muscles, and the thin, barely-there slits on his face where his nose would be flare slightly. The church is eerily quiet, especially here, above the old sanctuary, where mice and birds don't dare to nest, and even Karai holds her breath. This is the Shredder's room, and nobody enters without his permission, or his summoning.

Nobody except Karai.

She presses her thumb into the nerve at Donnie's elbow, and urges him forwards.

Even the water is still as she walks down the aisle, Donnie at her side. The fires are out, and only cheap orange streetlight pours through the windows.

Here, it's hard not to think of what could have been if she'd never learned the truth. Karai has been raised for this; with the Shredder dead, the Foot would by all rights bow to her. Right here in the nexus of all that power, it almost overwhelms her: how easy it would be, to return to her place at the right hand of her—

 _My daughter. Why won't you_ understand _me_?

The Shredder is _not_ her father.

(Had he loved her, once, as a man should love his daughter? The moments she remembers — being proud to be at his side, to have his trust and belief, to know that he relied on her as a soldier — these are tainted things now, like the memories of him bringing her trinkets, and him holding his large palm out as she punched it, and how only she was allowed to touch his scars, and how the words _my daughter_ filled her with pride and loyalty and fierce affection, even when they came to New York and he was lost to a vendetta _that he caused_ —

Had he looked at her every day and remembered the woman he murdered, as he lied about how she died?)

When Karai takes her seat in the throne, Donatello stands next to her, silent and still.

When he breathes, his teeth glimmer in the dark.

* * *

When the door to the throne room opens, light flooding in, Karai stretches languidly before draping her legs over the arm of the throne.

Everything is calculated. This room, this seat, this show of casual disrespect.

When Karai looks back at the years she spent at the Shredder's side, this was normal. She relished her position as the favourite, gently pushing at her boundaries, and what the Shredder would tolerate. Then, when it was time to go to work, she slipped skilfully into battle as the weapon she was made to be.

Oroku Saki does not always play the part of a mass murderer. Tonight, here, he is ever the businessman, no cape, no gauntlets, no Kuro Kabuto, just a tall, well-dressed man with an angrily-scarred face. The fabric of his shirt falls strangely on his arm — a bandage, maybe, over the wound left by her own blade

That doesn't make him any less dangerous. Just because his blades are no longer visible does not mean that they are no longer there. Hidden both in and out of plain sight, as all ninjas, and all weapons, should be.

"Karai."

The almost-softness in his voice repulses her.

The Shredder looks around the room, and in her mind's-eye, Karai can see how his guard rises and falls when he realises that Splinter is not with her, when he realises what is, and how she isn't spoiling for a fight.

"What is the meaning of this?" he asks.

Karai stretches out, the armrest of the throne digging into the backs of her thighs — this forced casualness, and cockiness, is no more than her behaving the way she's always behaved when being disobedient. As she stretches, she points her feet towards where Donnie is still standing, silent and still. "I brought you a friend."

Slowly, Donnie raises his head.

The Shredder's good eye widens — so slightly that Karai wonders if she is the only person who would have ever noticed it — and then narrows again as he takes stock of the situation.

If the Shredder takes this situation for what it is, he will reach for one of the many hidden blades he keeps, and this will be a fight, one which Karai knows will be difficult to escape from, never mind succeed.

But if he falls for it, even for a moment, then Karai has a shot.

It ends _tonight_.

The Shredder stays silent a moment longer. He has come into this room alone — no retainers, no Xever simpering behind him. Chris Bradford is with Stockman and the other two. Something catches in Karai's gut when she thinks about them, even briefly — they aren't stupid enough to come after her, not right now, when they could be curing the other three.

It was, after all, what she was counting on.

The Shredder takes in a slow lungful of air. "I see," he says. He takes another step forward, his dark eye analysing and re-analysing the situation, whether or not he's threatened here. Karai's heart speeds up, thumping rabbit-like in her chest.

Is he daring to _hope_? Karai has returned, with one of the turtles at her side, ready to fall into line and finish Hamato Yoshi off for good. It's almost so pathetic it has to be true.

"You two should get to know each-other," she says, swinging her legs back over the armrests until she's sitting upright. The Shredder's eye narrows through the gloom. Karai tilts her head to the left. "Hey Donnie," she says, pointing forward. "Aren't you hungry?"

"Karai—" the Shredder starts, as Donnie takes one step forward, and then another, his legs forming into long, snake-like tails.

 _What must we do with our enemies, Karai_? the Shredder said to her, years and years ago.

Donnie rises and rises, his legs coiling beneath him and blurring into one heavy body, tumbling faster and faster down the steps with his hands now hungry, frothing mouths. Karai leans forward, her hand reaching for her own blade.

"Karai, _enough_!"

Donnie hisses, and throws his scarred bulk forwards, jaws unhinging. The Shredder pulls a hidden blade and dodges the first strike. Donnie's sharp teeth gnash together as they miss their mark. Each smaller head lunges forward, twisting and writhing, and the Shredder dodges those too.

Karai draws her own blade silently. Donnie, hungry, angry, fights like a storm — there's no logic to him, no foresight or thought; all Donnie wants to do is to eat.

And maybe, somewhere in the basest part of him, Donnie wants to kill. The Shredder is an enemy, forged in blood and vengeance. Any one of the turtles hate him, Raph would want Shredder dead anyway, but Karai would put money on Donnie and Leo having done the math, knowing exactly to the dollar how much better off the world would be if he no longer existed. In her darkest moments in the church's basement, with her hands and nails bloody and tired, Karai has done the math too.

Donnie swipes high, aiming one set of jaws at the Shredder's head, and feints — no matter where the Shredder tries to go, there are always more teeth, full of ivory and venom and—

Steel.

Karai slashes at the Shredder's injured arm. She misses, her hands tight and sweaty on the hilt of her blade, and rears back for a second attempt, heart behind her teeth, and suddenly, the world tilts in the wrong direction, her legs smashed out from underneath her by a large tail.

 _No logic. No foresight._

Karai was once Donnie's enemy too.

Karai breaks her fall on her elbows, slamming the impact down through the ground, but Donnie, every inch of him, comes swarming towards her, jaws and teeth and spit.

So, this is what Leo meant.

There isn't time to laugh at the irony, or at how blind she was. There isn't even time to be _angry_ — or to wish for rescue as Donnie curls around her. Karai is tired of wishing.

"Karai!" the Shredder yells. Donnie's coils loosen and tighten, and it's that split-second that gives Karai what she needs. She flexes her wrist, letting a kunai drop from her sleeve, and shoves it deep into Donnie's side, the way she should have done to Mikey. Beneath the point, the skin cracks, then gives way, the kunai puncturing Donnie's flank and lodging there.

Donnie rears back, a sound like a rusted hinge shrieking from his throat, and then he jolts forwards, the scream stuttering, as the Shredder's blade finds its mark in his back.

Blood sprays across the floor.

* * *

April clues into the fact that Donnie's missing about a second after Casey does, and he watches her face twist into an ugly mix of shock, and horror, and _fury_.

Casey gets it.

Karai's played them. He'd always assumed that bringing Donnie here, they'd put him to work, doing his weird _Breaking Bad_ impression with all the beakers and science and nerd-stuff that he always has going on. But instead, Donnie just stood guard, and did nothing.

Now, Casey gets why. Donnie wasn't here for Stockman, Donnie was here for—

"Can you find them?" Casey asks April urgently, tapping at his head. She nods, her hands already reaching for her temples, then stops.

"Casey—" She stops, then tries again.

Casey watches her, his heart thumping high in his throat. A cold sweat prickles the hair on his top lip. "You can do this, Red," he encourages, and that does it — April cuts him a look, all piss and vinegar and _I_ know _I can do this_. He raises his hands in mock-surrender, offering her a tight smile because really, he gets it.

He wants to hope for the best with Karai — maybe she just took Donnie to the little psycho turtles' room — but his gut is already telling him what he doesn't want to know: Karai planned for this, and whatever she's taken Donnie to do, she needed a distraction first.

He really doesn't want to look at Chris Bradford's naked furry ass, but there it is, mooning the entire room. Stockman wasn't exactly giving him the four-star treatment when he chained him to a pipe.

"We need to cure the others," he says, more for himself than for her. "Then we go get Donnie. But we need to know where she took him."

He waits for April to argue. The way things are going, he almost surprised that April isn't throwing her hands in the air — _I knew she'd do this, Casey, you never listened to me, she's bad news! I knew she'd betray us! Do you even care?_ — and he'd yell right back at her — _Yeah, Red, I'm pissed off, is that what you want!?_

But she doesn't, because this is _serious business_ , make-or-break time, and he feels _shitty_ for doubting her at a time like this.

"Alright." April lifts her hands to her temples. "Let's do this."

* * *

It's not as easy to find someone as Casey thinks; not here, in the middle of the city, where the church is hidden in plain sight. The streets are full of people, taxis honking, trucks snarling, so it's hard to find the silent voices that April needs to listen to.

It's not like the cold, dark sewers and tunnels, with metres of stone above her head and so few lives below.

And it's hard to do anything when all April can focus on now is the roar in her blood demanding that she find Karai, _hunt her down_ , and bring Donnie back to where he is safe, with her, away from whatever plan it was Karai never told them about.

She curls her hands into fists and squeezes until her knuckles hurt, dragging up the memory of something Raph once said under his breath, when he had been told to sit and meditate on _calmness_ after he tried to fit his fist into Mikey's mouth: _like a river, over stone_.

She imagines that Raph is supposed to be the stone, large and immovable, with the river of little irritations flowing over his shell. But April imagines herself to be the _river_ , wearing down the porous rock until it either smoothes for her or shatters and is cast out to sea. The noise of the city likens to a river, voices chattering like rushing water, and here it's easy to see what she needs.

Xever is still lazing in his water feature. The ashigaru-sha have gone out, for either pizza or Neosporin. Rahzar lies in the corner of the laboratory, in a miserable, dead sleep. Casey waits impatiently while Stockman flits around.

In the heart of the old church, she finds Karai, and the hot, vicious confusion of Donnie's thoughts, and something else, something familiar.

Fire.

* * *

"Casey," April says, so pale that he can see each one of her freckles. "Casey, Shredder's in the building. Donnie, he's—"

Her voice breaks.

"He's _hurting_."

Casey presses his mouth together into a thin line until he can feel his lips tingle. "I'll call Splinter," he says.

* * *

Before he goes, Splinter looks to his wife and daughter.

Tang Shen still stares out of the photograph on the shrine, formal, stern, unforgiving. It is not just their daughter that Splinter has failed to save, but his — their — sons. Instead, by being what he has become, he has been forced to sit back, and let their daughter, their Miwa, take charge.

He is not proud of her. Not yet. There are things that she has done that are not acceptable in this clan, there are things that afterwards, when she has folded herself back into her rightful place alongside her brothers, she will learn, and what's left of the Foot will fade into nothing more than a distant memory for her.

He hopes.

Tang Shen had shown that the Hamato clan was where she wanted her daughter to be raised. Betrayal, false plans, false promises — these are all things that Miwa will learn to forget, at least when it comes to her own family.

He does not ask his wife to wish him luck. Luck is not something that this family is blessed with. Instead, it has its honour to fight for, and its legacy to protect, even in the shadows. Everything it has gotten, it has gotten though bloodied, scraped knuckles and hungry bellies and sheer force of will.

The wound in his foot is healing, albeit not as fast as he would like — the venom is almost purged, an ugly acid-yellow weeping from the crusting scab each time he lays his hands on it — but it is enough to serve this last purpose, leading his sons to their salvation.

And if there is no salvation, at least there will be rest for them.

This is not how he wanted his sons to die. This is not how any man would want their sons to die, minds lost, and lives lost at the hands of their father. But if the cure does not work, then perhaps this would be kinder, and then he would avenge them the way he should have avenged Tang Shen all those years ago, instead of hiding in a new land.

 _No_.

He as a father will not bury his sons.

He as a father will save them, as much as he can.

He blows the candle out, and turns towards the dojo shoji. His foot still hurts, stinging with each heavy step, stinging more whenever the scab cracks, and the closer he gets to his destination the more his gut gets heavy. Falling into line does not sit well with him after all these years, falling into line at his daughter's command sits worse, knowing what Karai's plan is, knowing what she is willing to say and do, to achieve her goals—

At the end of it, Karai's plan is to use her own father as bait to save her brothers.

He is willing to be that bait, if it means that his sons will start tomorrow back in themselves, as the four lights that led him from darkness over sixteen years ago.

Leonardo, Michelangelo and Donatello's bedrooms are empty. He does not go into them, but waits a second outside, listening to all that is not there. No sleeping sons, no videos, no reading, no brothers together. The quiet is unbearably loud.

And then, there is Raphael. Trapped in the snake form, and trapped in his own room.

Splinter has always tried not to take favourites; though some of his sons are better students than others, though some of his sons are impenetrable when it comes to understanding them, Raphael is the son Splinter has always worried about, the son who is too much like himself, from his temper to his fierce, loyal heart.

The sword hidden in his staff comes into use so rarely, but the blade is well-oiled and slips out of its hollow with no sound. There is no drama; a ninja is and always will be made for subtlety and silence. Splinter wraps his hand tightly around the blade and pulls up shortly. The steel slides through his skin, whisper-sharp and like a bitter, scalding ice as blood begins to bead into the wound.

Inside Raphael's room, he can hear his son moving, and imagines it in his mind's eye — the three heads lifting to the air, catching the scent of blood, their jaws unhinging and their stomachs roiling.

He moves before Raphael slams into his unlocked bedroom door, the blade unclean but safe in his staff. The bleeding is heavier now, blood flooding to the wound and oozing through it, out of his closed fist and down his wrist. It mats into the fur, beading into thick, fat drops that spatter across the concrete underfoot.

Raphael slams against his door. The scent of blood is in his nose now, and it will not be long before he breaks out and into the lair. Splinter picks up his pace, not stopping until he reaches the thick chain at the door to the laboratory.

He uses his staff, leveraging it into the heavy old padlock, and snaps the metal with a sharp jerk.

The door is open. His sons are free.

There is no laughter from Leonardo this time. Just hungry sounds as two bodies hurl themselves at the door, echoed by Raphael behind.

On the platform above the disused tracks, Splinter waits for a long moment, letting his blood plip gently to the floor. Raphael slams himself against his door, and in the laboratory, either Leonardo or Michelangelo start to pull at the door, the chain slipping loose with the force.

Then, almost perfectly timed, Raphael falls out of his room, lithe and long and full of bloodlust, and Michelangelo shoves his way past Leonardo, rising up and up, his long forked tongue snaking out of his mouth as he looks upon his father.

Splinter turns, drops to all fours, and runs. Out into the sewers, with the rest of the rats, and towards what could be the end of his sons.

* * *

 **tbc.**


	12. Part 12

tmnt is property of Viacom.

 _in this chapter:_ snurt to the left. snurt to the right. take it back now, y'all. one last time to get funky with it.

* * *

 **Birth of Serpents  
part 12**

* * *

 _"Marco!" Leonardo yells, his small voice so much louder here, in the older tunnels where Splinter takes them to play. The lair, although bigger than their old nest, is still too small for his sons, who need to run and climb and whatever else young boys must.  
_

 _Somewhere in another tunnel, another voice rings out: "Pooooooooooooooooooooolo!"_

 _Leonardo turns, sprints into another tunnel, and vanishes into the dark._

 _Splinter would like for his sons to have a playground — brightly-coloured swings, and slides and monkey-bars for them to climb all over, but instead they must make do here, with the best he can offer them. There are times he wonders: did he do the right thing in bringing them underground? Would it not have been better for him to steal a car, escape upstate, and become just another rumour in the forests? But he has to weigh the benefits — fresh air, nature, a place in the sun for his sons to bask and grow — with the downfalls: American winters are not kind, nor are Americans a generous people, not in the ways that matter. At least here, in New York, crime and coldness are unfortunate facts of life: nobody notices if a grocery store has been broken into, nobody cares if a homeless man talks about the creatures he's seen underground._

 _The New York Giant Rat is more than just a myth, but equally, there is more than just one type of New York Giant Rat._

 _Raphael runs past him, his feet slapping on the wet ground. "MARCO!" he yells, then yells louder as Michelangelo pounces on him from a ledge above. "That's not the game! Sensei!" He turns, still trying to pry Michelangelo off of his shell. "Sensei, tell him that's not the game!"_

 _"Adaptation is the hallmark of the ninja," Splinter says placidly — it is remarkable how often the 'because ninjas' excuse works._

 _(Though they are still only five.)_

 _"Ha!" Michelangelo crows, still clinging to Raphael, his chubby arms winding around his brother's neck and his toes curling into the bridge of his shell, and Raphael bears it all with the stoic tolerance of somebody who really doesn't quite mind. "See? I totally adapted you!"_

 _"Whatever, Mikey."_

 _Raphael folds his arms, the classic pose of one who is about to begin sulking, and so Splinter must intervene: "I seem to be missing two sons," he prompts. "Or does this mean that they have won this game?"_

 _"NO," Raphael yells, stamping a foot. "C'mon, Mikey!" He reaches over and grabs Michelangelo's fat wrist and drags him off._

 _"MAAAAAAAAARCO!" Michelangelo bellows, his voice echoing through the old damp brickwork._

 _In the distance, two other little voices snicker, their voices echoing off of the walls and through the tunnels. Splinter edges closer to the water — the rains have been particularly heavy, of late, and sometimes things wash down from the surface; pieces of flotsam to shore up their home; beaten, yet still useful, toys for his sons; a wallet, with money and credit cards._

 _It is a short while later when, while fishing out what looks to be a particularly warm, if filthy, scarf, a pair of sad, slow footsteps plap up to Splinter's side. When he looks down, blue and brown eyes stare up. Leonardo has his arm around Donatello's thin shoulders, as Donatello clutches his left hand in his right._

 _Donatello thankfully does not know yet the effect his eyes could have if appropriately weaponised; for now, he stands woefully in front of Splinter, brown eyes brimming with tears as he tries to be very, very brave, holding the torn skin up for his father to see. "I hurt myself," he says dolefully. The tear in his palm is long and ragged, shiny with blood and sewer slime. It will need to be thoroughly cleaned, with water as hot as Donatello can stand._

 _"Do you think it will need stitches?" Splinter asks — and is pleased when Donatello shakes his head. Donatello has already started to become somewhat of an amateur medic, always first on hand to deal with bumps and bruises and scratches and scrapes; in perhaps another year, Splinter thinks, it may be time to introduce him to the medicinal herbs that Splinter keeps in his room. "Would you like to go home?"_

 _Donatello hesitates. It is so rare that they are allowed out, and as much as he himself may want to leave, Donatello is not the type to try to spoil his brothers' fun._

 _Leonardo makes the decision for the three of them. He turns on his heel, cupping his hands around his mouth: "RAAAAAAAAAPH. MIKEY. GET BACK HERE. WE'RE GOIN' HOME."_

 _Two whines answer back through the tunnels._

 _Perhaps tomorrow's training, Splinter thinks, will focus on the need for_ stealth _, and_ silence _._

 _Donatello sniffs once, rubbing his forearm along his eyes. Splinter allows him this — they are not old enough, yet, to really talk about levels of pain, and thresholds, and especially not during play. "Then let us go home," he says instead, reaching down to rest a gentle, careful hand on Donatello's head. Donatello stretches up, trying to get as much affectionate contact as he can, and this, Splinter does not allow. He pulls his hand away, but can't help but look down, ready to deal with Donatello's miserable expression._

 _Instead, Donatello's face is slack, and slick green eyes stare back up at him._

* * *

Deep within the tunnels, Splinter opens his eyes.

His sons are close.

His trail brought them through the tunnels of New York, taking them the long route from their home out towards the Shredder's hideaway. As snakes, his sons are fast, but he is faster, and smaller, able to sneak through tight tunnels and collapsed brickwork, forcing them to work to hunt him down. Here, less than a street away from the church, he has to strain his ears to hear them, trying to focus on the whisper of snakeskin on tunnel, and willing away the tight clench in his heart. His sons are finally the silent, quiet hunters he wanted them to become, and yet he would give everything for them to be loud, and noisy, and _safe_.

In the darkness, water drips.

The sound ricochets off the walls, echoing down the tunnels.

Another drip. Ricochet. Echo.

Another. And then—

The echo returns, the sound wrong, bounced back from a breathing hide.

His sons are close.

Splinter eases himself back onto his feet. His bad leg aches from the cold and the exertion, but here, he has led his three sons to a drainage junction close to the old church. The water here is not just old rain and sweat from the streets above, but the remnants of the fire. It smells of sewage and soot. Directly above could be either their salvation or their damnation.

The art historian in him almost — _almost_ — wants to laugh.

"Sensei?" Leonardo asks. "We're hungry."

The soft, plaintive note in Leonardo's voice is too calculated to be real. Nonetheless it pulls at Splinter's heart, digging into memories of his small sons, hidden away from the world, with nothing but each-other.

 _I am sorry, my son_ , Splinter said once, so very very long ago, heavy with regret. _I have nothing to give you._

This time, Splinter steps out into the thin glimmer of streetlight that has trickled into the sewer. "Perhaps when we go home," he says, above Raphael's keen, hungry hissing, "we will eat then."

Leonardo makes a soft hum. "Or," he says, playing with the word as it hangs between them. "We could eat _now_."

Behind him, Michelangelo smiles, jaw lax and teeth sharp, and Leonardo steps aside as Michelangelo steps forward, to take point.

Is this a kindness? Splinter wonders. Feeding the youngest, caring for the baby, the way his sons always do.

Either way, Splinter takes a step back, and then another. "We know what you're doing," Leonardo says. "We know what _Donatello_ has been doing."

This, Splinter had guessed, and yet, he asks despite himself. "And what is that?"

Leonardo's smile is cold, and cruel, and Splinter does not need to hear the words underneath it, nor the implication.

"You have always been very intelligent, my son," he says instead.

All three of his sons blink once. Then, one by one, their eyes shutter, pupils narrowing to a tight, hungry focus. The fur rises on the back of Splinter's neck, and he is more than ready when Michelangelo launches first, teeth bared and throat rasping.

Splinter dodges, fending off Michelangelo's reforming hand with a sharp chop to his wrist, then pivots.

Michelangelo is already there.

Splinter does not have time to think of all the ways Michelangelo could be an impressive ninja if he _cared_ to do so. Instead, he dips, ducking out of the way of Michelangelo's hungry jaws and leading his youngest son into Raphael's way. Michelangelo rears back, one of his smaller heads reaching out and smacking Raphael firmly across the back of the head. Raphael slinks back, momentarily cowed, before rearing up again.

Jaws come at him from either side, from above and below, from front to back, and Splinter dodges them all; the tunnel is small, the space is tight, and his sons are hungry, and unfocused. Splinter seizes a rusted metal rebar and thrusts it between Leonardo's jaws a heartbeat before Leonardo's teeth impale his arm. Splinter uses the control to wring Leonardo's body like a thick piece of string. A kick with his good foot knocks the wind out of Raphael, and both he and Leonardo are twisted into Michelangelo's rising bulk.

As they slump together, stunned, Splinter looks down at the seething ball.

His three boys, knotted together. They hiss and snarl and spit, twisting against each-other. Leonardo strains out of the ball, his body half-reforming as he reaches a hand towards Splinter.

Splinter slams his foot into Leonardo's fingers.

"If you want me, you will know where to find me," he says, and boosts himself upwards towards the street.

* * *

"Okay," April says. "We're all set."

Casey turns around from where he's been swinging his hockey stick into a nearby cabinet, trying to smack it with the quietest _thump_. It's one of the few exercises Splinter has taught him, all about how to _control_ the power behind each blow, and knowing when to exact _precision_ , not _pain_.

He doesn't agree with all of that, but what he does agree with is the murder-look April gave him when he smacked the cabinet too hard, the flat metallic _thlank_ echoing around the lab loud enough to make her jump. Casey Jones likes staying alive.

But Casey Jones also likes _not waiting_.

He feels it in his shoulders — the denied promise of a fight, the beatings that he _owes_ Shredder, the one he's _really_ tempted to give Karai for pulling this shit; it itches and pulls at his muscles all at the same time, running down to his fingers until his fingers find nothing and he has to flex them once, twice, running a slow count of all the people he's going to beat down when this is over.

Shredder. Karai. Stockbug. Raph, just because.

 _Raph_.

Right now, Raph, the big cuddly snuggle-snake from hell, is either chasing his giant rat dad/dinner through a tunnel, or he and his brothers are chowing down on their giant rat dad/dinner.

Vaguely, he's aware of just _how metal_ the mental image is — giant snake monsters, covered in blood, tearing into their prey — it's like something off of a Norwegian Bear Troll Death Scream album, but then the thought sours in his gut – this is _fucked up_.

They're not snake monsters. They're supposed to be his _friends_.

"Yeah?" Casey asks. "Good."

The retromutagen has all been carefully poured into canisters — something Snotman wouldn't let anybody near until April casually reminded him who was in charge, and Casey made a helpful ripping-off-wings gesture. Then, they loaded it into ghetto guns made out of old caulking tubes — nothing fancy, but enough to squirt a giant snake in the face.

And now, they have to wait.

He checks his phone again, counting the minutes since he last spoke to Splinter.

When Casey called, he figured Splinter already had enough to deal with, what with Raph, and Mikey, and Leo, King of the Corn Children, so all he said was that Karai had gone AWOL, and taken Donnie with her.

Which was bad enough.

Telling Splinter _also, Red thinks that Donnie is being ripped to shreds right now_ was something that probably wouldn't help. Raph always makes a pissy comment about how Leo is _Splinter's favourite_ and how Mikey _gets away with everything_ , but if Splinter is anything like Casey's own dad— Casey's been in a lot more trouble for a lot longer than his little sister has, but he knows full well that his big old bear of a hockey-player dad would _rip through a building_ if he knew Casey was in trouble.

It's a lie, Casey knows, but one that he figures is more ninja than asshole. Not telling Splinter that his kid might be dead means that Splinter might be able to get the other three here to be cured without being turned into snake-chow.

 _Sorry, Dee,_ Casey thinks, and tells himself he'll make it up to Donnie when this is all over, by getting him the _really_ good fertiliser from Home Depot.

Sighing, he turns back to April. "How long you think til Splinter gets here?"

April doesn't reply.

Casey whips around, ready to smush some bug across the floor if Stockman's tried any of his weird tricks, but instead, the giant flyman is just peering at where April has zoned out, again. "Red," Casey calls. April ignores him, her face blank and slack, and her eyes a freaky off-white. "Red!"

"Sorry," April slurs, coming back to herself. "I was just—"

"Using your Dondar, yeah, I figured."

"Don't be an asshole, Casey."

Casey bites back the flirt — _aw Red, I thought that was how you liked me_ — and settles for a smirk instead. "He doin' okay?" he asks, then wishes he hadn't from the look on her face. It's clear, now, that Donnie isn't doing too great.

And Casey hates it but he can't squash the run of jealousy in his gut: would April be like this for him?

He'd like to think so.

Above, one of the windows cracks open, and a slim shape slips in, effectively changing the subject. "Master Splinter," April breathes, getting to her feet. "Are you okay?"

Splinter drops gracefully to the floor — until he lands, when his injured foot takes the brunt of the landing, and all six-foot-whatever of muscle-bound rat staggers to the side. Casey instantly reaches an arm out, trying to steady him, and almost buckles under the weight when Splinter presses a hand into his shoulder. "I am fine," he says, and Casey does not say _dude, you are totally not fine_ , but he is definitely thinking it. "They are coming. Is everything ready?"

"Hai, sensei," April says, turning away from them to pick up one of the thrown-together retromutagen guns Stockman built. "We already tested it. It works."

Across the room, Chris Bradford huffs a big, sleepy dog sigh, his leg kicking under the tarp Casey threw over his ass. "Also, we got them dinner," he says, jerking a thumb in Bradford's direction.

Splinter's whiskers lift, though Casey isn't sure if it's in amusement or — most likely — irritation, but whatever, the joke was solid. He tenses his shoulder until Splinter lets go, then rotates it as Rat Dad glides across the room. "Good." He glances at the fly to April's left. "Baxter Stockman, I presume," he says, then doesn't pay attention to whatever response he gets. "Where is Karai?"

Casey interjects before April can say _literally anything_. "Still not back yet."

"And Donatello?"

"With Karai."

"Sensei—" April starts. Casey steels himself — here is where April tells Splinter about how Donnie is bleeding out somewhere on Shredder's fist, how Donnie has been stuck on one of Shredder's spikes like a weird creepy tribute, how all she can feel from him is _pain_ — but Splinter interrupts her before she can say anything:

"She did not tell you of this plan?" Splinter says.

"Nope," Casey replies.

"Or any other plan," April snots in. Casey winces.

"I see," Splinter says, but doesn't say anything else.

Outside, a car alarm goes off.

April goes very still. "They're here," she says.

They all brace for impact, but it's not enough to _really_ prepare them as the three snakes smash through a window, each landing in a coil on the floor. Glass rains down around them. Mikey shakes his heads like a dog, and then settles back into his coils.

Three big, green turds, Casey thinks, and clutches his hockey stick a little bit tighter. He looks over to Raph, no longer quiet and cowed, but angry and hungry, and it feels like someone kicked him in the gut with both misery and anger — this is going to _end_ , one way or another.

As one, the three turtles raise their heads, green eyes wide and noses tilted towards the ceiling. They sniff the air delicately, and all three of them break into identical, fanged grins.

* * *

Splinter takes one step backwards. "My sons," he says, but the turtles ignore him. Raph and Leo take the lead, their eyes bright green and their mouths open, hissing slowly, eager to begin their meal.

April glances to Casey, tilting her head back towards the canisters of retromutagen. Carefully, she sidles backwards, hand reaching out and almost sighing in relief as Stockman presses a dispenser into her hand. She almost doesn't even care about the sticky, tacky mucus his hands have left on the barrel, nor the fetid stink his wings beat in her direction.

The turtles might speak, but April doesn't listen; instead, she focuses all of her senses on Splinter, waiting for him to move out of the way, for her, and Casey, and Stockman to take their shots.

She wonders which of his brothers tore into Donnie the most, and presses her finger more readily against the trigger.

Something in Leo's face breaks, his eyes slitting, and he launches himself at Raph. Mikey takes advantage of their distraction, and starts to shift towards Splinter, shoulders and head low, his green eyes hooded.

Above, a door slams open, and everything stops.

From a balcony, the Shredder stares down, Karai at his side, cowed and silent.

"Saki." Splinter turns, glaring upwards.

"I was wondering how long it would take before you came crawling back," Shredder says. He hefts the lump on his shoulder.

It takes a long, long moment for April to realise that the lump is _Donnie_ , and longer still to realise that the Shredder has thrown him from the balcony, her eyes tracking him as Donnie tumbles gracelessly to the floor. The noise his plastron makes against the old floors echoes around the space, and he takes in a sharp, gasping breath, waking up for the smallest moment — and like that, the quiet, stunned spell is broken. Agony blooms across April's vision, thick and strong, and her legs buckle beneath her, her head swimming and chest pounding with everything released from Donnie's head — pain, and _panic_ , and the stringy, pathetic thrum of a heart struggling to beat.

It's only when Casey hauls her back, bodily, that April realises that she's already five steps into a sprint across the room. " _Casey let me go_!" she shrieks, bucking against him, which only makes him tense his arms and pull her in close, her back to his chest. " _Donnie_!"

The worst of it all is, the pain she feels from Donnie; his pain, his terror, the hot writhing snake-like twist of his mind — they're nothing compared to the sight of his body.

Gashes are torn down his arms and legs, his face already swelling with the bruises along his cheek and head. The bridge on his side is weeping with blood from an open stab wound and, worst of all, his shell is cracked wide-open, a great cavern of flesh and blood.

* * *

 _Rage_.

Rage is an emotion Splinter knows well — a double-edged sword that, when used effectively, can give a man the strength of a thousand others, but if used incorrectly, can damn him a thousand times over and over. It is a lesson he has tried to impress on Raphael his entire life; the strength in those big fists was one that needs to be controlled, harnessed, primed — like a bomb, waiting for the perfect moment to step off the trigger and destroy everything — not himself.

The rage he feels right now is enough to destroy half of New York, were he to let it out.

Saki has murdered his wife, stole his daughter, chased him from his homeland, and now, when Splinter has finally reached a strange resignation, a quiet _peace_ with his lot in life — no, his family will never have what they truly deserve, but they have a _life_ together, and his sons are inching their ways into the world making friends and allies and making a difference, in their own way — Saki came again, with fire, and steel, and a vicious thirst for revenge. Saki hurt his sons. Saki has hunted them down, and now—

Donatello drags in a rasping, hissing breath, his arms and feet trembling, smearing his own blood along the cracked tiles.

— now, his gentle boy lies dying on the floor. His remaining sons are wild and untamed things, and above it all, wreathed in fire, the man who was once his brother watches it all, Splinter's daughter in his grasp.

Rage is the only thing Splinter has room for in his heart. _Control_ is all he will allow for it.

He focuses that control at the man who was once his brother.

"Saki!" Splinter roars.

Across the room, the Shredder inclines his head — the only sign that he has listened to what Splinter has said. At Splinter's back, his sons hiss, hungry and angry, though even they seem to know that this is something they should not interfere with. "Release my daughter," Splinter demands.

Even from across the room, even though the motion is so small he can barely see it, Splinter knows Saki well-enough to know that his grip would have tightened, fingers wrapped firmly around Miwa's arm, and Splinter spares a glance to his daughter, forcing down the anger that rises in his chest — that her disobedience, her need for hatred and revenge, has forced their hand this way. But the time for reprimands will come later, when this is over. For now, he meets her eyes, impressing on her the need to do as he says, to be obedient for the next few minutes while they finish what should have been finished long ago.

"No," the Shredder says. "She is _my_ daughter."

"That is not true."

Miwa does not make a sound. Even though her arms are tense, even as she leans away from the Shredder's grip; but Miwa is well-trained, knowing when not to struggle, and when to pick her moment. "Karai is _not yours_ ," the Shredder spits. " _I_ was the one who raised her, cared for her while you were hiding in _filth_. _I_ was the one who taught her everything she knows. She is _mine_."

"She is not." Splinter forces down the possessiveness that flares up. Miwa is _his_ daughter, it is him that she has called _father_ , it is _his blood_ that runs in her veins. "She is _Shen's_ daughter. Release her."

"So you and your youkai can poison her with more of your lies?"

"My _sons_ have told her nothing more than the truth. Where is your honour? Let Miwa go."

It is so easy to goad the Shredder into this, baiting him out of his high ground advantage, and into Splinter's claws and fists and teeth. He sees it in his sons, the way brothers know each-other as intimately as they know themselves; a word, a gesture, a look, can all press buttons that others do not even see.

The man who was once his brother laughs once. " _You_ talk of _honour_?" he spits. "What does a _rat_ know of _honour_?"

"More than a man who murdered a woman and stole her daughter away." Splinter carefully eases his weight onto his good leg. "More than a man who waged war against my sons — against mere _boys_."

"Look at those creatures you call _sons_. Demons. _Freaks_. You claim them as family but they share none of your blood."

"No," Splinter agrees. "Neither did you, and yet you were still my brother." The talk of demons — of _youkai_ — is something Splinter has not heard from his brother in decades, and for a brief, half-moment, he remembers the brother he loved, and pities him and his broken mind, to still think about spirits when — "The only demon in this room, Saki, is you. Let my daughter go. Cure my sons. Let us end this as men, not monsters. Shen would not want this of either of us."

"What would you know about what Shen wanted? You never deserved her. Always so obsessed with your clan. She _needed_ you, and you turned her back; you failed her just like you have failed these _sons_ of yours."

Splinter ignores the comment about his sons, even though it is right. Splinter has failed them in this. But unlike the Shredder, Splinter knows the feeling and weight of heavy failure on his shoulders, and how to bear its weight. No matter what happens at the end of tonight, he will go home alive, and take stock of his new burdens.

"Shen was my _wife_." Splinter carefully notes the path that the Shredder will take — down to the floor, past Donatello, a juggernaut made flesh. And Splinter carefully notes the advantages he has here; speed, agility, _calmness_ amid the chaos that his three other sons will no doubt cause once this fragile, glass-thin stillness is broken. It is in this chaos, this frenzy, that April and Casey will have their chance to cure the others.

"I loved her first."

"You do not know how to love," Splinter shoots back. "Even now. Tell me, Saki, do you love my daughter, or do you love what she represents to you? A victory. A _prize_."

"Enough!"

"You love my daughter no more than you loved _my wife_."

The careful calculation pays off. Saki thrusts his arms out, shoving Miwa off-balance and out of his grasp. She stumbles to the side and slinks back towards the shadows— unarmed, but that can be changed; what matters is that for the immediate time being she is safe as Saki rants: "You did _not_ love Tang Shen! You wanted to keep her in a cage. What about what _Shen_ wanted? She wanted to leave you. Where was she living, before you murdered her? _Away_ from you, and from that filth of a clan. And how many times," the Shredder snarls, "did she come to my bed? You _left her_. You _abandoned_ her. You _never deserved her_."

Splinter draws himself up to his full height; shoulders square, arms lax at his sides — pride, though it comes before a fall, can be so very satisfying. "And yet, in the end, she still chose me," he says, and waits for Saki to come.

* * *

 **tbc. we're almost done.**


End file.
